Introduction To

Introduction to
SQL
SQL is a standard language for accessing and manipulating databases.
What is SQL?
 SQL stands for Structured Query Language
 SQL lets you access and manipulate databases
 SQL became a standard of the American National Standards Institute
(ANSI) in 1986, and of the International Organization for Standardization
(ISO) in 1987
What Can SQL do?

 SQL can execute queries against a database
 SQL can retrieve data from a database
 SQL can insert records in a database
 SQL can update records in a database
 SQL can delete records from a database
 SQL can create new databases
 SQL can create new tables in a database
 SQL can create stored procedures in a database
 SQL can create views in a database
 SQL can set permissions on tables, procedures, and views
SQL is a Standard - BUT....

Although SQL is an ANSI/ISO standard, there are different versions of the SQL
language.
However, to be compliant with the ANSI standard, they all support at least the
major commands (such as SELECT, UPDATE, DELETE, INSERT, WHERE) in a similar
manner.
Note: Most of the SQL database programs also have their own proprietary
extensions in addition to the SQL standard!
Using SQL in Your Web Site
To build a web site that shows data from a database, you will need:
 An RDBMS database program (i.e. MS Access, SQL Server, MySQL)

 To use a server-side scripting language, like PHP or ASP
 To use SQL to get the data you want
 To use HTML / CSS to style the page
RDBMS
RDBMS stands for Relational Database Management System.
RDBMS is the basis for SQL, and for all modern database systems such as MS
SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.
The data in RDBMS is stored in database objects called tables. A table is a

collection of related data entries and it consists of columns and rows.
Look at the "Customers" table:
Example
SELECT * FROM Customers;
Try it Yourself »
Every table is broken up into smaller entities called fields. The fields in the
Customers table consist of CustomerID, CustomerName, ContactName,
Address, City, PostalCode and Country. A field is a column in a table that is
designed to maintain specific information about every record in the table.
A record, also called a row, is each individual entry that exists in a table. For
example, there are 91 records in the above Customers table. A record is a
horizontal entity in a table.
A column is a vertical entity in a table that contains all information

associated
witth a specific field in a table.
SQL Syntax
Database Tables
A database most often contains one or more tables. Each table is identified by a
name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data.
In this tutorial we will use the well-known Northwind sample database (included
in MS Access and MS SQL Server).
Below is a selection from the "Customers" table:
CustomerI CustomerName ContactName Address City PostalCode Country

D
1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2 Ana Trujillo Ana Trujillo Avda. de la México 05021 Mexico

Emparedados y Constitución D.F.
helados 2222
3 Antonio Moreno Antonio Mataderos 2312 México 05023 Mexico

Taquería Moreno D.F.
4 Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK
5 Berglunds Christina Berguvsvägen 8 Luleå S-958 22 Sweden
snabbköp Berglund
The table above contains five records (one for each customer) and seven
columns (CustomerID, CustomerName, ContactName, Address, City,
PostalCode, and Country).
SQL Statements
Most of the actions you need to perform on a database are done with SQL
statements.
The following SQL statement selects all the records in the "Customers" table:
Example
Try it Yourself »
RUN SQL
In this tutorial we will teach you all about the different SQL statements.
Keep in Mind That...

 SQL keywords are NOT case sensitive: select is the same as SELECT
In this tutorial we will write all SQL keywords in upper-case.
Semicolon after SQL Statements?

Some database systems require a semicolon at the end of each SQL statement.
Semicolon is the standard way to separate each SQL statement in database

systems that allow more than one SQL statement to be executed in the same
call to the server.
In this tutorial, we will use semicolon at the end of each SQL statement.
Some of The Most Important SQL

Commands
 SELECT - extracts data from a database
 UPDATE - updates data in a database
 DELETE - deletes data from a database
 INSERT INTO - inserts new data into a database
 CREATE DATABASE - creates a new database
 ALTER DATABASE - modifies a database
 CREATE TABLE - creates a new table
 ALTER TABLE - modifies a table
 DROP TABLE - deletes a table
 CREATE INDEX - creates an index (search key)
 DROP INDEX - deletes an index
SQL SELECT Statement
The SQL SELECT Statement
The SELECT statement is used to select data from a database.
The data returned is stored in a result table, called the result-set.
SELECT Syntax
SELECT column1, column2, ...
FROM table_name;
Here, column1, column2, ... are the field names of the table you want to select
data from. If you want to select all the fields available in the table, use the
following syntax:
SELECT * FROM table_name;
Demo Database
Below is a selection from the "Customers" table in the Northwind sample
database:
CustomerI CustomerName ContactName Address City PostalCod Country

D e

helados 2222


snabbköp Berglund
SELECT Column Example
The following SQL statement selects the "CustomerName" and "City" columns
from the "Customers" table:
Example
SELECT CustomerName, City FROM Customers;
Try it Yourself »
SELECT * Example
The following SQL statement selects all the columns from the "Customers"
table:
Example
Try it Yourself »
RUN SQL
SQL SELECT DISTINCT Statement
The SQL SELECT DISTINCT Statement
The SELECT DISTINCT statement is used to return only distinct (different)
values.
Inside a table, a column often contains many duplicate values; and sometimes
you only want to list the different (distinct) values.
SELECT DISTINCT Syntax

SELECT DISTINCT column1, column2, ...
FROM table_name;
Demo Database
database:
CustomerID CustomerName ContactName Address City PostalCode Country

helados 2222


snabbköp Berglund
SELECT Example Without DISTINCT

The following SQL statement selects all (including the duplicates) values from
the "Country" column in the "Customers" table:
Example
SELECT Country FROM Customers;
Try it Yourself »
Now, let us use the SELECT DISTINCT statement and see the result.
SELECT DISTINCT Examples

The following SQL statement selects only the DISTINCT values from the
"Country" column in the "Customers" table:
Example
SELECT DISTINCT Country FROM Customers;
Try it Yourself »
RUN SQL
The following SQL statement lists the number of different (distinct) customer
countries:
Example
SELECT COUNT(DISTINCT Country) FROM Customers;
Try it Yourself »
Note: The example above will not work in Firefox! Because

COUNT(DISTINCT column_name) is not supported in Microsoft Access
databases. Firefox is using Microsoft Access in our examples.
Here is the workaround for MS Access:

Example
SELECT Count(*) AS DistinctCountries
FROM (SELECT DISTINCT Country FROM Customers);
Try it Yourself »
SQL WHERE Clause
The SQL WHERE Clause
The WHERE clause is used to filter records.
It is used to extract only those records that fulfill a specified condition.
WHERE Syntax
FROM table_name
WHERE condition;
Note: The WHERE clause is not only used in SELECT statements, it is also used

in UPDATE, DELETE, etc.!
Demo Database
database:

helados 2222

5 Berglunds snabbköp Christina Berguvsvägen 8 Luleå S-958 22 Sweden

Berglund
WHERE Clause Example

The following SQL statement selects all the customers from the country
"Mexico", in the "Customers" table:
Example
SELECT * FROM Customers
WHERE Country='Mexico';
Try it Yourself »
Text Fields vs. Numeric Fields

SQL requires single quotes around text values (most database systems will also
allow double quotes).
However, numeric fields should not be enclosed in quotes:
Example
WHERE CustomerID=1;
Try it Yourself »
Operators in The WHERE Clause
The following operators can be used in the WHERE clause:
Operator Description Example
= Equal Try it
> Greater than Try it
< Less than Try it
>= Greater than or equal Try it
<= Less than or equal Try it
<> Not equal. Note: In some versions of SQL this operator Try it

may be written as !=
BETWEEN Between a certain range Try it
LIKE Search for a pattern Try it

IN To specify multiple possible values for a column
SQL AND, OR and
NOT Operators
The SQL AND, OR and NOT Operators
The WHERE clause can be combined with AND, OR, and NOT operators.
The AND and OR operators are used to filter records based on more than one

condition:
 The AND operator displays a record if all the conditions separated

by AND are TRUE.
 The OR operator displays a record if any of the conditions separated
by OR is TRUE.
The NOT operator displays a record if the condition(s) is NOT TRUE.
AND Syntax
FROM table_name
WHERE condition1 AND condition2 AND condition3 ...;
OR Syntax
FROM table_name
WHERE condition1 OR condition2 OR condition3 ...;
NOT Syntax
FROM table_name
WHERE NOT condition;
Demo Database
The table below shows the complete "Customers" table from the Northwind
sample database:
CustomerI CustomerNa ContactName Address City PostalCod Country
D me e
1 Alfreds Maria Anders Obere Str. 57 Berlin 12209 Germany

Futterkiste
2 Ana Trujillo Ana Trujillo Avda. de la México D.F. 05021 Mexico

Emparedados Constitución
y helados 2222
3 Antonio Antonio Mataderos México D.F. 05023 Mexico

Moreno Moreno 2312
Taquería
4 Around the Thomas Hardy 120 Hanover London WA1 1DP UK

Horn Sq.
5 Berglunds Christina Berguvsvägen Luleå S-958 22 Sweden

snabbköp Berglund 8
6 Blauer See Hanna Moos Forsterstr. 57 Mannheim 68306 Germany

Delikatessen
7 Blondel père Frédérique 24, place Strasbourg 67000 France

et fils Citeaux Kléber
8 Bólido Martín C/ Araquil, 67 Madrid 28023 Spain

Comidas Sommer
preparadas
9 Bon app' Laurence 12, rue des Marseille 13008 France

Lebihans Bouchers
10 Bottom-Dollar Elizabeth 23 Tsawassen Tsawassen T2F 8M4 Canada

Marketse Lincoln Blvd.
11 B's Beverages Victoria Fauntleroy London EC2 5NT UK

Ashworth Circus
12 Cactus Patricio Cerrito 333 Buenos 1010 Argentina

Comidas para Simpson Aires
llevar
13 Centro Francisco Sierras de México D.F. 05022 Mexico

comercial Chang Granada 9993
Moctezuma
14 Chop-suey Yang Wang Hauptstr. 29 Bern 3012 Switzerlan

Chinese d
15 Comércio Pedro Afonso Av. dos São Paulo 05432- Brazil

Mineiro Lusíadas, 23 043
16 Consolidated Elizabeth Berkeley London WX1 6LT UK

Holdings Brown Gardens 12
Brewery
17 Drachenblut Sven Ottlieb Walserweg 21 Aachen 52066 Germany

Delikatessend
18 Du monde Janine 67, rue des Nantes 44000 France

entier Labrune Cinquante
Otages
19 Eastern Ann Devon 35 King London WX3 6FW UK

Connection George
20 Ernst Handel Roland Kirchgasse 6 Graz 8010 Austria

Mendel
21 Familia Aria Cruz Rua Orós, 92 São Paulo 05442- Brazil

Arquibaldo 030
22 FISSA Fabrica Diego Roel C/ Madrid 28034 Spain

Inter. Moralzarzal,
Salchichas 86
S.A.
23 Folies Martine 184, chaussée Lille 59000 France

gourmandes Rancé de Tournai
24 Folk och fä HB Maria Larsson Åkergatan 24 Bräcke S-844 67 Sweden
25 Frankenversa Peter Franken Berliner Platz München 80805 Germany

nd 43
26 France Carine Schmitt 54, rue Royale Nantes 44000 France

restauration
27 Franchi S.p.A. Paolo Accorti Via Monte Torino 10100 Italy

Bianco 34
28 Furia Lino Jardim das Lisboa 1675 Portugal

Bacalhau e Rodriguez rosas n. 32
Frutos do Mar
29 Galería del Eduardo Rambla de Barcelona 08022 Spain

gastrónomo Saavedra Cataluña, 23
30 Godos Cocina José Pedro C/ Romero, Sevilla 41101 Spain

Típica Freyre 33
31 Gourmet André Av. Brasil, 442 Campinas 04876- Brazil

Lanchonetes Fonseca 786
32 Great Lakes Howard 2732 Baker Eugene 97403 USA

Food Market Snyder Blvd.
33 GROSELLA- Manuel 5ª Ave. Los Caracas 1081 Venezuela
Restaurante Pereira Palos Grandes
34 Hanari Carnes Mario Pontes Rua do Paço, Rio de 05454- Brazil

67 Janeiro 876
35 HILARIÓN- Carlos Carrera 22 San 5022 Venezuela

Abastos Hernández con Ave. Cristóbal
Carlos
Soublette #8-
35
36 Hungry Yoshi Latimer City Center Elgin 97827 USA

Coyote Import Plaza 516
Store Main St.
37 Hungry Owl Patricia 8 Johnstown Cork Ireland

All-Night McKenna Road
Grocers
38 Island Trading Helen Bennett Garden House Cowes PO31 7PJ UK

Crowther
Way
39 Königlich Philip Cramer Maubelstr. 90 Brandenbur 14776 Germany

Essen g
40 La corne Daniel Tonini 67, avenue de Versailles 78000 France

d'abondance l'Europe
41 La maison Annette 1 rue Alsace- Toulouse 31000 France

d'Asie Roulet Lorraine
42 Laughing Yoshi 1900 Oak St. Vancouver V3F 2K1 Canada

Bacchus Wine Tannamuri
Cellars
43 Lazy K John Steel 12 Orchestra Walla Walla 99362 USA

Kountry Store Terrace
44 Lehmanns Renate Magazinweg 7 Frankfurt 60528 Germany

Marktstand Messner a.M.
45 Let's Stop N Jaime Yorres 87 Polk St. San 94117 USA

Shop Suite 5 Francisco
46 LILA- Carlos Carrera 52 Barquisimet 3508 Venezuela

Supermercad González con Ave. o
o Bolívar #65-
98 Llano
Largo
47 LINO- Felipe Ave. 5 de I. de 4980 Venezuela

Delicateses Izquierdo Mayo Margarita
Porlamar
48 Lonesome Fran Wilson 89 Portland 97219 USA
Pine Chiaroscuro
Restaurant Rd.
49 Magazzini Giovanni Via Ludovico il Bergamo 24100 Italy

Alimentari Rovelli Moro 22
Riuniti
50 Maison Catherine Rue Joseph- Bruxelles B-1180 Belgium

Dewey Dewey Bens 532
51 Mère Jean Fresnière 43 rue St. Montréal H1J 1C3 Canada

Paillarde Laurent
52 Morgenstern Alexander Heerstr. 22 Leipzig 04179 Germany

Gesundkost Feuer
53 North/South Simon South House London SW7 1RZ UK

Crowther 300
Queensbridge
54 Océano Yvonne Ing. Gustavo Buenos 1010 Argentina

Atlántico Ltda. Moncada Moncada Aires
8585 Piso 20-
A
55 Old World Rene Phillips 2743 Bering Anchorage 99508 USA

Delicatessen St.
56 Ottilies Henriette Mehrheimerst Köln 50739 Germany
Käseladen Pfalzheim r. 369
57 Paris Marie 265, Paris 75012 France

spécialités Bertrand boulevard
Charonne
58 Pericles Guillermo Calle Dr. Jorge México D.F. 05033 Mexico

Comidas Fernández Cash 321
clásicas
59 Piccolo und Georg Pipps Geislweg 14 Salzburg 5020 Austria

mehr
60 Princesa Isabel de Estrada da Lisboa 1756 Portugal

Isabel Vinhoss Castro saúde n. 58
61 Que Delícia Bernardo Rua da Rio de 02389- Brazil

Batista Panificadora, Janeiro 673
12
62 Queen Lúcia Carvalho Alameda dos São Paulo 05487- Brazil

Cozinha Canàrios, 891 020
63 QUICK-Stop Horst Kloss Taucherstraß Cunewalde 01307 Germany

e 10
64 Rancho Sergio Av. del Buenos 1010 Argentina
grande Gutiérrez Libertador Aires
900
65 Rattlesnake Paula Wilson 2817 Milton Albuquerqu 87110 USA

Canyon Dr. e
Grocery
66 Reggiani Maurizio Strada Reggio 42100 Italy

Caseifici Moroni Provinciale Emilia
124
67 Ricardo Janete Limeira Av. Rio de 02389- Brazil

Adocicados Copacabana, Janeiro 890
267
68 Richter Michael Holz Grenzacherw Genève 1203 Switzerlan

Supermarkt eg 237 d
69 Romero y Alejandra Gran Vía, 1 Madrid 28001 Spain

tomillo Camino
70 Santé Jonas Erling Skakkes Stavern 4110 Norway

Gourmet Bergulfsen gate 78
71 Save-a-lot Jose Pavarotti 187 Suffolk Boise 83720 USA

Markets Ln.
72 Seven Seas Hari Kumar 90 Wadhurst London OX15 4NB UK
Imports Rd.
73 Simons bistro Jytte Petersen Vinbæltet 34 København 1734 Denmark
74 Spécialités du Dominique 25, rue Paris 75016 France

monde Perrier Lauriston
75 Split Rail Beer Art P.O. Box 555 Lander 82520 USA
& Ale Braunschweig
er
76 Suprêmes Pascale Boulevard Charleroi B-6000 Belgium

délices Cartrain Tirou, 255
77 The Big Liz Nixon 89 Jefferson Portland 97201 USA

Cheese Way Suite 2
78 The Cracker Liu Wong 55 Grizzly Butte 59801 USA

Box Peak Rd.
79 Toms Karin Josephs Luisenstr. 48 Münster 44087 Germany

Spezialitäten
80 Tortuga Miguel Angel Avda. Azteca México D.F. 05033 Mexico

Restaurante Paolino 123
81 Tradição Anabela Av. Inês de São Paulo 05634- Brazil
Hipermercado Domingues Castro, 414 030
s
82 Trail's Head Helvetius 722 DaVinci Kirkland 98034 USA

Gourmet Nagy Blvd.
Provisioners
83 Vaffeljernet Palle Ibsen Smagsløget Århus 8200 Denmark

45
84 Victuailles en Mary Saveley 2, rue du Lyon 69004 France

stock Commerce
85 Vins et alcools Paul Henriot 59 rue de Reims 51100 France

Chevalier l'Abbaye
86 Die Rita Müller Adenaueralle Stuttgart 70563 Germany

Wandernde e 900
Kuh
87 Wartian Pirkko Torikatu 38 Oulu 90110 Finland

Herkku Koskitalo
88 Wellington Paula Parente Rua do Resende 08737- Brazil

Importadora Mercado, 12 363
89 White Clover Karl Jablonski 305 - 14th Seattle 98128 USA
Markets Ave. S. Suite
3B
90 Wilman Kala Matti Keskuskatu 45 Helsinki 21240 Finland

Karttunen
91 Wolski Zbyszek ul. Filtrowa 68 Walla 01-012 Poland
AND Example
The following SQL statement selects all fields from "Customers" where country
is "Germany" AND city is "Berlin":
Example
WHERE Country='Germany' AND City='Berlin';
Try it Yourself »
OR Example
The following SQL statement selects all fields from "Customers" where city is
"Berlin" OR "München":
Example
WHERE City='Berlin' OR City='München';
Try it Yourself »
is "Germany" OR "Spain":
Example
WHERE Country='Germany' OR Country='Spain';
Try it Yourself »
NOT Example
is NOT "Germany":
Example
WHERE NOT Country='Germany';
Try it Yourself »
Combining AND, OR and NOT

You can also combine the AND, OR and NOT operators.
is "Germany" AND city must be "Berlin" OR "München" (use parenthesis to form
complex expressions):
Example
WHERE Country='Germany' AND (City='Berlin' OR City='München');
Try it Yourself »
is NOT "Germany" and NOT "USA":
Example
WHERE NOT Country='Germany' AND NOT Country='USA';
Try it Yourself »
SQL ORDER BY Keyword
The SQL ORDER BY Keyword
The ORDER BY keyword is used to sort the result-set in ascending or descending
order.
The ORDER BY keyword sorts the records in ascending order by default. To sort

the records in descending order, use the DESC keyword.
ORDER BY Syntax
FROM table_name
ORDER BY column1, column2, ... ASC|DESC;
Demo Database
database:

D e

helados 2222

snabbköp Berglund
ORDER BY Example
The following SQL statement selects all customers from the "Customers" table,
sorted by the "Country" column:
Example
ORDER BY Country;
Try it Yourself »
ORDER BY DESC Example

sorted DESCENDING by the "Country" column:
Example
ORDER BY Country DESC;
Try it Yourself »
ORDER BY Several Columns Example

sorted by the "Country" and the "CustomerName" column. This means that it
orders by Country, but if some rows have the same Country, it orders them by
CustomerName:
Example
ORDER BY Country, CustomerName;
Try it Yourself »
ORDER BY Several Columns Example 2

sorted ascending by the "Country" and descending by the "CustomerName"
column:
Example
ORDER BY Country ASC, CustomerName DESC;
Try it Yourself »
SQL INSERT INTO Statement
The SQL INSERT INTO Statement
The INSERT INTO statement is used to insert new records in a table.
INSERT INTO Syntax

It is possible to write the INSERT INTO statement in two ways:
1. Specify both the column names and the values to be inserted:
INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);
2. If you are adding values for all the columns of the table, you do not need to
specify the column names in the SQL query. However, make sure the order of
the values is in the same order as the columns in the table. Here, the INSERT
INTO syntax would be as follows:
INSERT INTO table_name
VALUES (value1, value2, value3, ...);
Demo Database
database:

D
89 White Clover Karl Jablonski 305 - 14th Ave. S. Seattle 98128 USA
Markets Suite 3B
90 Wilman Kala Matti Keskuskatu 45 Helsink 21240 Finland

Karttunen i
INSERT INTO Example

The following SQL statement inserts a new record in the "Customers" table:
Example
INSERT INTO Customers (CustomerName, ContactName, Address, City,
PostalCode, Country)
VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen
21', 'Stavanger', '4006', 'Norway');
Try it Yourself »
The selection from the "Customers" table will now look like this:
CustomerID CustomerName ContactName Address City PostalCod Country

e
89 White Clover Karl Jablonski 305 - 14th Ave. Seattle 98128 USA
Markets S. Suite 3B

Karttunen
92 Cardinal Tom B. Skagen 21 Stavanger 4006 Norway

Erichsen
Did you notice that we did not insert any number into the CustomerID
field?
The CustomerID column is an auto-increment field and will be generated
automatically when a new record is inserted into the table.
Insert Data Only in Specified Columns

It is also possible to only insert data in specific columns.
The following SQL statement will insert a new record, but only insert data in the
"CustomerName", "City", and "Country" columns (CustomerID will be updated
automatically):
Example
INSERT INTO Customers (CustomerName, City, Country)
VALUES ('Cardinal', 'Stavanger', 'Norway');
Try it Yourself »

D
89 White Clover Karl Jablonski 305 - 14th Ave. S. Seattle 98128 USA
Markets Suite 3B

Karttunen
92 Cardinal null null Stavanger null Norway
SQL NULL Values
What is a NULL Value?
A field with a NULL value is a field with no value.
If a field in a table is optional, it is possible to insert a new record or update a

record without adding a value to this field. Then, the field will be saved with a
NULL value.
Note: A NULL value is different from a zero value or a field that contains
spaces. A field with a NULL value is one that has been left blank during record
creation!
How to Test for NULL Values?

It is not possible to test for NULL values with comparison operators, such as =,
<, or <>.
We will have to use the IS NULL and IS NOT NULL operators instead.
IS NULL Syntax
SELECT column_names
FROM table_name
WHERE column_name IS NULL;
IS NOT NULL Syntax

SELECT column_names
FROM table_name
WHERE column_name IS NOT NULL;
Demo Database
database:
e

helados 2222


Berglund
The IS NULL Operator

The IS NULL operator is used to test for empty values (NULL values).
The following SQL lists all customers with a NULL value in the "Address" field:
Example
SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NULL;
Try it Yourself »
Tip: Always use IS NULL to look for NULL values.
The IS NOT NULL Operator

The IS NOT NULL operator is used to test for non-empty values (NOT NULL
values).
The following SQL lists all customers with a value in the "Address" field:
Example
SELECT CustomerName, ContactName, Address
FROM Customers
WHERE Address IS NOT NULL;
Try it Yourself »
SQL UPDATE Statement
The SQL UPDATE Statement
The UPDATE statement is used to modify the existing records in a table.
UPDATE Syntax
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;
Note: Be careful when updating records in a table! Notice the WHERE clause in

the UPDATE statement. The WHERE clause specifies which record(s) that should be
updated. If you omit the WHERE clause, all records in the table will be updated!
Demo Database
database:

D e

Emparedados y Constitución 2222 D.F.
helados


Berglund
UPDATE Table
The following SQL statement updates the first customer (CustomerID = 1) with
a new contact person and a new city.
Example
UPDATE Customers
SET ContactName = 'Alfred Schmidt', City= 'Frankfurt'
WHERE CustomerID = 1;
Try it Yourself »
1 Alfreds Futterkiste Alfred Schmidt Obere Str. 57 Frankfurt 12209 Germany

helados 2222

snabbköp Berglund
UPDATE Multiple Records

It is the WHERE clause that determines how many records will be updated.
The following SQL statement will update the ContactName to "Juan" for all
records where country is "Mexico":
Example
UPDATE Customers
SET ContactName='Juan'
WHERE Country='Mexico';
Try it Yourself »
1 Alfreds Futterkiste Alfred Schmidt Obere Str. 57 Frankfurt 12209 Germany

2 Ana Trujillo Juan Avda. de la México 05021 Mexico
helados 2222
3 Antonio Moreno Juan Mataderos 2312 México 05023 Mexico

Taquería D.F.

snabbköp Berglund
Update Warning!
Be careful when updating records. If you omit the WHERE clause, ALL records will
be updated!
Example
UPDATE Customers
SET ContactName='Juan';
Try it Yourself »
1 Alfreds Futterkiste Juan Obere Str. 57 Frankfurt 12209 Germany
2 Ana Trujillo Juan Avda. de la México 05021 Mexico

helados 2222
3 Antonio Moreno Juan Mataderos 2312 México 05023 Mexico

Taquería D.F.
4 Around the Horn Juan 120 Hanover Sq. London WA1 1DP UK
5 Berglunds Juan Berguvsvägen 8 Luleå S-958 22 Sweden

snabbköp
SQL DELETE Statement
The SQL DELETE Statement
The DELETE statement is used to delete existing records in a table.
DELETE Syntax
DELETE FROM table_name WHERE condition;
Note: Be careful when deleting records in a table! Notice the WHERE clause in
the DELETE statement. The WHERE clause specifies which record(s) should be
deleted. If you omit the WHERE clause, all records in the table will be deleted!
Demo Database
database:

D

helados 2222


snabbköp Berglund
SQL DELETE Example
The following SQL statement deletes the customer "Alfreds Futterkiste" from the
"Customers" table:
Example
DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';
Try it Yourself »
The "Customers" table will now look like this:

e

helados 2222


snabbköp Berglund
Delete All Records
It is possible to delete all rows in a table without deleting the table. This means
that the table structure, attributes, and indexes will be intact:
DELETE FROM table_name;
The following SQL statement deletes all rows in the "Customers" table, without
deleting the table:
Example
DELETE FROM Customers;
Try it Yourself »
SQL TOP, LIMIT, FETCH FIRST or

ROWNUM Clause
The SQL SELECT TOP Clause
The SELECT TOP clause is used to specify the number of records to return.
The SELECT TOP clause is useful on large tables with thousands of records.

Returning a large number of records can impact performance.
Note: Not all database systems support the SELECT TOP clause. MySQL supports

the LIMIT clause to select a limited number of records, while Oracle uses FETCH
FIRST n ROWS ONLY and ROWNUM.
SQL Server / MS Access Syntax:

SELECT TOP number|percent column_name(s)
FROM table_name
WHERE condition;
MySQL Syntax:
SELECT column_name(s)
FROM table_name
WHERE condition
LIMIT number;
Oracle 12 Syntax:
FROM table_name
ORDER BY column_name(s)
FETCH FIRST number ROWS ONLY;
Older Oracle Syntax:
FROM table_name
WHERE ROWNUM <= number;
Older Oracle Syntax (with ORDER BY):
SELECT *
FROM (SELECT column_name(s) FROM table_name ORDER BY column_name(s))
WHERE ROWNUM <= number;
Demo Database
database:

D

helados 2222


snabbköp Berglund
SQL TOP, LIMIT and FETCH FIRST

Examples
The following SQL statement selects the first three records from the
"Customers" table (for SQL Server/MS Access):
Example
SELECT TOP 3 * FROM Customers;
Try it Yourself »
The following SQL statement shows the equivalent example for MySQL:
Example
LIMIT 3;
Try it Yourself »
The following SQL statement shows the equivalent example for Oracle:
Example
FETCH FIRST 3 ROWS ONLY;
SQL TOP PERCENT Example
The following SQL statement selects the first 50% of the records from the
"Customers" table (for SQL Server/MS Access):
Example
SELECT TOP 50 PERCENT * FROM Customers;
Try it Yourself »
Example
FETCH FIRST 50 PERCENT ROWS ONLY;
ADD a WHERE CLAUSE

The following SQL statement selects the first three records from the
"Customers" table, where the country is "Germany" (for SQL Server/MS
Access):
Example
SELECT TOP 3 * FROM Customers
WHERE Country='Germany';
Try it Yourself »
The following SQL statement shows the equivalent example for MySQL:
Example
WHERE Country='Germany'
LIMIT 3;
Try it Yourself »
Example
FETCH FIRST 3 ROWS ONLY;
SQL MIN() and MAX() Functions
The SQL MIN() and MAX() Functions
The MIN() function returns the smallest value of the selected column.
The MAX() function returns the largest value of the selected column.
MIN() Syntax
SELECT MIN(column_name)
FROM table_name
WHERE condition;
MAX() Syntax
SELECT MAX(column_name)
FROM table_name
WHERE condition;
Demo Database
Below is a selection from the "Products" table in the Northwind sample
database:
ProductID ProductName SupplierID CategoryID Unit Price
1 Chais 1 1 10 boxes x 20 bags 18
2 Chang 1 1 24 - 12 oz bottles 19
3 Aniseed Syrup 1 2 12 - 550 ml bottles 10
4 Chef Anton's Cajun Seasoning 2 2 48 - 6 oz jars 22
5 Chef Anton's Gumbo Mix 2 2 36 boxes 21.35
MIN() Example
The following SQL statement finds the price of the cheapest product:
Example
SELECT MIN(Price) AS SmallestPrice
FROM Products;
Try it Yourself »
MAX() Example
The following SQL statement finds the price of the most expensive product:
Example
SELECT MAX(Price) AS LargestPrice
FROM Products;
Try it Yourself »
SQL COUNT(), AVG() and

SUM() Functions
The SQL COUNT(), AVG() and SUM()
Functions
The COUNT() function returns the number of rows that matches a specified
criterion.
COUNT() Syntax
SELECT COUNT(column_name)
FROM table_name
WHERE condition;
The AVG() function returns the average value of a numeric column.
AVG() Syntax
SELECT AVG(column_name)
FROM table_name
WHERE condition;
The SUM() function returns the total sum of a numeric column.

SUM() Syntax
SELECT SUM(column_name)
FROM table_name
WHERE condition;
Demo Database
database:

COUNT() Example
The following SQL statement finds the number of products:
Example
SELECT COUNT(ProductID)
FROM Products;
Try it Yourself »
Note: NULL values are not counted.
AVG() Example
The following SQL statement finds the average price of all products:
Example
SELECT AVG(Price)
FROM Products;
Try it Yourself »
Note: NULL values are ignored.

Demo Database
Below is a selection from the "OrderDetails" table in the Northwind sample
database:
OrderDetailID OrderID ProductID Quantity
1 10248 11 12
2 10248 42 10
3 10248 72 5
4 10249 14 9
5 10249 51 40
SUM() Example
The following SQL statement finds the sum of the "Quantity" fields in the
"OrderDetails" table:
Example
SELECT SUM(Quantity)
FROM OrderDetails;
Try it Yourself »
Note: NULL values are ignored.
SQL LIKE Operator
The SQL LIKE Operator
The LIKE operator is used in a WHERE clause to search for a specified pattern in a
column.
There are two wildcards often used in conjunction with the LIKE operator:
 The percent sign (%) represents zero, one, or multiple characters

 The underscore sign (_) represents one, single character
Note: MS Access uses an asterisk (*) instead of the percent sign (%), and a
question mark (?) instead of the underscore (_).
The percent sign and the underscore can also be used in combinations!
LIKE Syntax
FROM table_name
WHERE columnN LIKE pattern;
Tip: You can also combine any number of conditions using AND or OR operators.
Here are some examples showing different LIKE operators with '%' and '_'
wildcards:
LIKE Operator Description
WHERE CustomerName LIKE Finds any values that start with "a"
'a%'
WHERE CustomerName LIKE Finds any values that end with "a"
'%a'
WHERE CustomerName LIKE Finds any values that have "or" in any position
'%or%'
WHERE CustomerName LIKE Finds any values that have "r" in the second position
'_r%'
WHERE CustomerName LIKE Finds any values that start with "a" and are at least 2
'a_%' characters in length
WHERE CustomerName LIKE Finds any values that start with "a" and are at least 3
'a__%' characters in length
WHERE ContactName LIKE 'a Finds any values that start with "a" and ends with "o"
%o'
Demo Database
sample database:

D

Futterkiste

Emparedados y Constitución
helados 2222

Moreno Moreno 2312
Taquería

Horn Sq.

snabbköp Berglund

Delikatessen
7 Blondel père et Frédérique 24, place Kléber Strasbourg 67000 France
fils Citeaux
8 Bólido Comidas Martín Sommer C/ Araquil, 67 Madrid 28023 Spain

preparadas

Lebihans Bouchers


Ashworth Circus
12 Cactus Comidas Patricio Cerrito 333 Buenos Aires 1010 Argentina

para llevar Simpson

Moctezuma
14 Chop-suey Yang Wang Hauptstr. 29 Bern 3012 Switzerland

Chinese
15 Comércio Pedro Afonso Av. dos São Paulo 05432-043 Brazil

Mineiro Lusíadas, 23

Brewery

Delikatessend
18 Du monde Janine Labrune 67, rue des Nantes 44000 France

entier Cinquante
Otages
19 Eastern Ann Devon 35 King George London WX3 6FW UK

Connection
20 Ernst Handel Roland Mendel Kirchgasse 6 Graz 8010 Austria
21 Familia Aria Cruz Rua Orós, 92 São Paulo 05442-030 Brazil

Arquibaldo
22 FISSA Fabrica Diego Roel C/ Moralzarzal, Madrid 28034 Spain

Inter. 86
Salchichas S.A.
23 Folies Martine Rancé 184, chaussée Lille 59000 France

gourmandes de Tournai
25 Frankenversand Peter Franken Berliner Platz München 80805 Germany

43

restauration

Bianco 34
28 Furia Bacalhau Lino Rodriguez Jardim das Lisboa 1675 Portugal

e Frutos do Mar rosas n. 32

30 Godos Cocina José Pedro C/ Romero, 33 Sevilla 41101 Spain

Típica Freyre
31 Gourmet André Fonseca Av. Brasil, 442 Campinas 04876-786 Brazil

Lanchonetes
32 Great Lakes Howard Snyder 2732 Baker Eugene 97403 USA
Food Market Blvd.
33 GROSELLA- Manuel Pereira 5ª Ave. Los Caracas 1081 Venezuela

Restaurante Palos Grandes
34 Hanari Carnes Mario Pontes Rua do Paço, 67 Rio de 05454-876 Brazil

Janeiro
35 HILARIÓN- Carlos Carrera 22 con San Cristóbal 5022 Venezuela

Abastos Hernández Ave. Carlos
Soublette #8-35
36 Hungry Coyote Yoshi Latimer City Center Elgin 97827 USA

Import Store Plaza 516 Main
St.
37 Hungry Owl All- Patricia 8 Johnstown Cork Ireland

Night Grocers McKenna Road

Crowther Way
39 Königlich Essen Philip Cramer Maubelstr. 90 Brandenburg 14776 Germany

41 La maison Annette Roulet 1 rue Alsace- Toulouse 31000 France

d'Asie Lorraine

Cellars
43 Lazy K Kountry John Steel 12 Orchestra Walla Walla 99362 USA

Store Terrace

45 Let's Stop N Jaime Yorres 87 Polk St. Suite San 94117 USA
Shop 5 Francisco
46 LILA- Carlos González Carrera 52 con Barquisimeto 3508 Venezuela

Supermercado Ave. Bolívar
#65-98 Llano
Largo
47 LINO- Felipe Izquierdo Ave. 5 de Mayo I. de 4980 Venezuela

Delicateses Porlamar Margarita
48 Lonesome Pine Fran Wilson 89 Chiaroscuro Portland 97219 USA

Restaurant Rd.
49 Magazzini Giovanni Rovelli Via Ludovico il Bergamo 24100 Italy

Alimentari Moro 22
Riuniti
50 Maison Dewey Catherine Rue Joseph- Bruxelles B-1180 Belgium

Dewey Bens 532
51 Mère Paillarde Jean Fresnière 43 rue St. Montréal H1J 1C3 Canada
Laurent

Gesundkost Feuer

Crowther 300
Queensbridge
54 Océano Yvonne Ing. Gustavo Buenos Aires 1010 Argentina

Atlántico Ltda. Moncada Moncada 8585
Piso 20-A
55 Old World Rene Phillips 2743 Bering St. Anchorage 99508 USA
Delicatessen
56 Ottilies Henriette Mehrheimerstr. Köln 50739 Germany

Käseladen Pfalzheim 369
57 Paris spécialités Marie Bertrand 265, boulevard Paris 75012 France

Charonne

clásicas

mehr
60 Princesa Isabel Isabel de Castro Estrada da Lisboa 1756 Portugal

Vinhoss saúde n. 58
61 Que Delícia Bernardo Rua da Rio de 02389-673 Brazil

Batista Panificadora, Janeiro
12
62 Queen Cozinha Lúcia Carvalho Alameda dos São Paulo 05487-020 Brazil
Canàrios, 891
63 QUICK-Stop Horst Kloss Taucherstraße Cunewalde 01307 Germany

10
64 Rancho grande Sergio Av. del Buenos Aires 1010 Argentina

Gutiérrez Libertador 900
65 Rattlesnake Paula Wilson 2817 Milton Dr. Albuquerque 87110 USA

Canyon Grocery
66 Reggiani Maurizio Strada Reggio Emilia 42100 Italy

Caseifici Moroni Provinciale 124
67 Ricardo Janete Limeira Av. Rio de 02389-890 Brazil

Adocicados Copacabana, Janeiro
267
68 Richter Michael Holz Grenzacherweg Genève 1203 Switzerland

Supermarkt 237

tomillo Camino
70 Santé Gourmet Jonas Erling Skakkes Stavern 4110 Norway

Bergulfsen gate 78
71 Save-a-lot Jose Pavarotti 187 Suffolk Ln. Boise 83720 USA

Markets

Imports Rd.

75 Split Rail Beer & Art P.O. Box 555 Lander 82520 USA
Ale Braunschweiger
76 Suprêmes Pascale Cartrain Boulevard Charleroi B-6000 Belgium

délices Tirou, 255
77 The Big Cheese Liz Nixon 89 Jefferson Portland 97201 USA

Way Suite 2
78 The Cracker Box Liu Wong 55 Grizzly Peak Butte 59801 USA
Rd.

Spezialitäten

81 Tradição Anabela Av. Inês de São Paulo 05634-030 Brazil

Hipermercados Domingues Castro, 414
82 Trail's Head Helvetius Nagy 722 DaVinci Kirkland 98034 USA
Gourmet Blvd.
Provisioners
83 Vaffeljernet Palle Ibsen Smagsløget 45 Århus 8200 Denmark

stock Commerce

Chevalier l'Abbaye
86 Die Wandernde Rita Müller Adenauerallee Stuttgart 70563 Germany

Kuh 900
87 Wartian Herkku Pirkko Koskitalo Torikatu 38 Oulu 90110 Finland
88 Wellington Paula Parente Rua do Resende 08737-363 Brazil

Importadora Mercado, 12
Markets S. Suite 3B
90 Wilman Kala Matti Karttunen Keskuskatu 45 Helsinki 21240 Finland

SQL LIKE Examples

The following SQL statement selects all customers with a CustomerName
starting with "a":
Example
WHERE CustomerName LIKE 'a%';
Try it Yourself »
The following SQL statement selects all customers with a CustomerName ending
with "a":
Example
WHERE CustomerName LIKE '%a';
Try it Yourself »
The following SQL statement selects all customers with a CustomerName that
have "or" in any position:
Example
WHERE CustomerName LIKE '%or%';
Try it Yourself »
have "r" in the second position:
Example
WHERE CustomerName LIKE '_r%';
Try it Yourself »
starts with "a" and are at least 3 characters in length:
Example
WHERE CustomerName LIKE 'a__%';
Try it Yourself »
The following SQL statement selects all customers with a ContactName that
starts with "a" and ends with "o":
Example
WHERE ContactName LIKE 'a%o';
Try it Yourself »
does NOT start with "a":
Example
WHERE CustomerName NOT LIKE 'a%';
Try it Yourself »
SQL Wildcards
SQL Wildcard Characters
A wildcard character is used to substitute one or more characters in a string.
Wildcard characters are used with the LIKE operator. The LIKE operator is used

in a WHERE clause to search for a specified pattern in a column.
Wildcard Characters in MS Access
Symbo Description Example

l
* Represents zero or more characters bl* finds bl, black, blue, and blob
? Represents a single character h?t finds hot, hat, and hit
[] Represents any single character h[oa]t finds hot and hat, but not hit
within the brackets
! Represents any character not in the h[!oa]t finds hit, but not hot and hat
brackets
- Represents any single character c[a-b]t finds cat and cbt

within the specified range
# Represents any single numeric 2#5 finds 205, 215, 225, 235, 245,
character 255, 265, 275, 285, and 295
Wildcard Characters in SQL Server
Symbol Description Example
% Represents zero or more characters bl% finds bl, black, blue, and
blob
_ Represents a single character h_t finds hot, hat, and hit
[] Represents any single character within the h[oa]t finds hot and hat, but
brackets not hit
^ Represents any character not in the h[^oa]t finds hit, but not hot
brackets and hat
- Represents any single character within the c[a-b]t finds cat and cbt
specified range
All the wildcards can also be used in combinations!
Here are some examples showing different LIKE operators with '%' and '_'
wildcards:
LIKE Operator Description

WHERE CustomerName LIKE Finds any values that starts with "a"
'a%'
WHERE CustomerName LIKE Finds any values that ends with "a"
'%a'
WHERE CustomerName LIKE Finds any values that have "or" in any position
'%or%'
WHERE CustomerName LIKE Finds any values that have "r" in the second position
'_r%'
WHERE CustomerName LIKE Finds any values that starts with "a" and are at least 3
'a__%' characters in length
WHERE ContactName LIKE 'a Finds any values that starts with "a" and ends with "o"
%o'
Demo Database
sample database:
CustomerI CustomerNam ContactName Address City PostalCod Country

D e e
Futterkiste

Emparedados y Constitución
helados 2222

Moreno Moreno 2312
Taquería

Horn Sq.
5 Berglunds Christina Berguvsvägen Luleå S-958 22 Sweden

snabbköp Berglund 8

Delikatessen
7 Blondel père et Frédérique 24, place Strasbourg 67000 France

fils Citeaux Kléber
8 Bólido Comidas Martín C/ Araquil, 67 Madrid 28023 Spain

preparadas Sommer

Lebihans Bouchers


Ashworth Circus
12 Cactus Patricio Cerrito 333 Buenos 1010 Argentina

Comidas para Simpson Aires
llevar

Moctezuma
14 Chop-suey Yang Wang Hauptstr. 29 Bern 3012 Switzerlan

Chinese d
15 Comércio Pedro Afonso Av. dos São Paulo 05432-043 Brazil

Mineiro Lusíadas, 23

Brewery

Delikatessend
18 Du monde Janine Labrune 67, rue des Nantes 44000 France

entier Cinquante
Otages
19 Eastern Ann Devon 35 King George London WX3 6FW UK

Connection
20 Ernst Handel Roland Mendel Kirchgasse 6 Graz 8010 Austria
21 Familia Aria Cruz Rua Orós, 92 São Paulo 05442-030 Brazil

Arquibaldo
22 FISSA Fabrica Diego Roel C/ Moralzarzal, Madrid 28034 Spain

Inter. 86
Salchichas S.A.
23 Folies Martine Rancé 184, chaussée Lille 59000 France

gourmandes de Tournai
25 Frankenversan Peter Franken Berliner Platz München 80805 Germany

d 43
restauration

Bianco 34
28 Furia Bacalhau Lino Rodriguez Jardim das Lisboa 1675 Portugal

e Frutos do rosas n. 32
Mar

30 Godos Cocina José Pedro C/ Romero, 33 Sevilla 41101 Spain

Típica Freyre
31 Gourmet André Fonseca Av. Brasil, 442 Campinas 04876-786 Brazil

Lanchonetes
32 Great Lakes Howard Snyder 2732 Baker Eugene 97403 USA

Food Market Blvd.
33 GROSELLA- Manuel Pereira 5ª Ave. Los Caracas 1081 Venezuela

Restaurante Palos Grandes
34 Hanari Carnes Mario Pontes Rua do Paço, Rio de 05454-876 Brazil

67 Janeiro
35 HILARIÓN- Carlos Carrera 22 con San 5022 Venezuela

Abastos Hernández Ave. Carlos Cristóbal
Soublette #8-
35
36 Hungry Coyote Yoshi Latimer City Center Elgin 97827 USA

Import Store Plaza 516 Main
St.
37 Hungry Owl Patricia 8 Johnstown Cork Ireland

All-Night McKenna Road
Grocers

Crowther Way
39 Königlich Essen Philip Cramer Maubelstr. 90 Brandenbur 14776 Germany

g

41 La maison Annette Roulet 1 rue Alsace- Toulouse 31000 France

d'Asie Lorraine
Cellars
43 Lazy K Kountry John Steel 12 Orchestra Walla Walla 99362 USA

Store Terrace

45 Let's Stop N Jaime Yorres 87 Polk St. San 94117 USA

Shop Suite 5 Francisco
46 LILA- Carlos Carrera 52 con Barquisimet 3508 Venezuela

Supermercado González Ave. Bolívar o
#65-98 Llano
Largo
47 LINO- Felipe Ave. 5 de I. de 4980 Venezuela

Delicateses Izquierdo Mayo Margarita
Porlamar
48 Lonesome Pine Fran Wilson 89 Chiaroscuro Portland 97219 USA

Restaurant Rd.
49 Magazzini Giovanni Via Ludovico il Bergamo 24100 Italy

Alimentari Rovelli Moro 22
Riuniti
50 Maison Dewey Catherine Rue Joseph- Bruxelles B-1180 Belgium
Dewey Bens 532
51 Mère Paillarde Jean Fresnière 43 rue St. Montréal H1J 1C3 Canada
Laurent

Gesundkost Feuer

Crowther 300
Queensbridge
54 Océano Yvonne Ing. Gustavo Buenos 1010 Argentina

Atlántico Ltda. Moncada Moncada 8585 Aires
Piso 20-A
55 Old World Rene Phillips 2743 Bering St. Anchorage 99508 USA
Delicatessen
56 Ottilies Henriette Mehrheimerstr Köln 50739 Germany

Käseladen Pfalzheim . 369
57 Paris Marie Bertrand 265, boulevard Paris 75012 France

spécialités Charonne

clásicas

mehr
60 Princesa Isabel Isabel de Estrada da Lisboa 1756 Portugal

Vinhoss Castro saúde n. 58
61 Que Delícia Bernardo Rua da Rio de 02389-673 Brazil

Batista Panificadora, Janeiro
12
62 Queen Cozinha Lúcia Carvalho Alameda dos São Paulo 05487-020 Brazil
Canàrios, 891
63 QUICK-Stop Horst Kloss Taucherstraße Cunewalde 01307 Germany

10
64 Rancho grande Sergio Av. del Buenos 1010 Argentina

Gutiérrez Libertador 900 Aires
65 Rattlesnake Paula Wilson 2817 Milton Albuquerqu 87110 USA

Canyon Dr. e
Grocery
66 Reggiani Maurizio Strada Reggio 42100 Italy

Caseifici Moroni Provinciale 124 Emilia
67 Ricardo Janete Limeira Av. Rio de 02389-890 Brazil

Adocicados Copacabana, Janeiro
267
68 Richter Michael Holz Grenzacherwe Genève 1203 Switzerlan

Supermarkt g 237 d

tomillo Camino
70 Santé Gourmet Jonas Erling Skakkes Stavern 4110 Norway

Bergulfsen gate 78
71 Save-a-lot Jose Pavarotti 187 Suffolk Ln. Boise 83720 USA

Markets

Imports Rd.

75 Split Rail Beer Art P.O. Box 555 Lander 82520 USA
& Ale Braunschweige
r
76 Suprêmes Pascale Boulevard Charleroi B-6000 Belgium

délices Cartrain Tirou, 255
77 The Big Cheese Liz Nixon 89 Jefferson Portland 97201 USA

Way Suite 2
78 The Cracker Liu Wong 55 Grizzly Peak Butte 59801 USA

Box Rd.

Spezialitäten

81 Tradição Anabela Av. Inês de São Paulo 05634-030 Brazil

Hipermercados Domingues Castro, 414
82 Trail's Head Helvetius Nagy 722 DaVinci Kirkland 98034 USA

Gourmet Blvd.
Provisioners
83 Vaffeljernet Palle Ibsen Smagsløget 45 Århus 8200 Denmark

stock Commerce

Chevalier l'Abbaye
86 Die Rita Müller Adenauerallee Stuttgart 70563 Germany

Wandernde 900
Kuh
87 Wartian Pirkko Torikatu 38 Oulu 90110 Finland

Herkku Koskitalo
88 Wellington Paula Parente Rua do Resende 08737-363 Brazil

Importadora Mercado, 12
Markets S. Suite 3B

Karttunen

Using the % Wildcard
The following SQL statement selects all customers with a City starting with
"ber":
Example
WHERE City LIKE 'ber%';
Try it Yourself »
The following SQL statement selects all customers with a City containing the
pattern "es":
Example
WHERE City LIKE '%es%';
Try it Yourself »
Using the _ Wildcard
The following SQL statement selects all customers with a City starting with any
character, followed by "ondon":
Example
WHERE City LIKE '_ondon';
Try it Yourself »
The following SQL statement selects all customers with a City starting with "L",
followed by any character, followed by "n", followed by any character, followed
by "on":
Example
WHERE City LIKE 'L_n_on';
Try it Yourself »
Using the [charlist] Wildcard
The following SQL statement selects all customers with a City starting with "b",
"s", or "p":
Example
WHERE City LIKE '[bsp]%';
Try it Yourself »
The following SQL statement selects all customers with a City starting with "a",
"b", or "c":
Example
WHERE City LIKE '[a-c]%';
Try it Yourself »
Using the [!charlist] Wildcard
The two following SQL statements select all customers with a City NOT starting
with "b", "s", or "p":
Example
WHERE City LIKE '[!bsp]%';
Try it Yourself »
Or:
Example
WHERE City NOT LIKE '[bsp]%';
Try it Yourself »
SQL IN Operator
The SQL IN Operator
The IN operator allows you to specify multiple values in a WHERE clause.
The IN operator is a shorthand for multiple OR conditions.
IN Syntax
FROM table_name
WHERE column_name IN (value1, value2, ...);
or:
FROM table_name
WHERE column_name IN (SELECT STATEMENT);
Demo Database
sample database:
Custom CustomerName ContactName Address City PostalCod Coun

erID e try
1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germ

any
2 Ana Trujillo Ana Trujillo Avda. de la Constitución México 05021 Mexi

Emparedados y 2222 D.F. co
helados
3 Antonio Moreno Antonio Mataderos 2312 México 05023 Mexi

Taquería Moreno D.F. co
5 Berglunds snabbköp Christina Berguvsvägen 8 Luleå S-958 22 Swed

Berglund en
6 Blauer See Hanna Moos Forsterstr. 57 Mannh 68306 Germ

Delikatessen eim any
7 Blondel père et fils Frédérique 24, place Kléber Strasbo 67000 Franc
Citeaux urg e
8 Bólido Comidas Martín C/ Araquil, 67 Madrid 28023 Spain

preparadas Sommer
9 Bon app' Laurence 12, rue des Bouchers Marseill 13008 Franc
Lebihans e e
10 Bottom-Dollar Elizabeth 23 Tsawassen Blvd. Tsawass T2F 8M4 Cana

Marketse Lincoln en da
11 B's Beverages Victoria Fauntleroy Circus London EC2 5NT UK
Ashworth
12 Cactus Comidas Patricio Cerrito 333 Buenos 1010 Arge

para llevar Simpson Aires ntina
13 Centro comercial Francisco Sierras de Granada 9993 México 05022 Mexi

Moctezuma Chang D.F. co
14 Chop-suey Chinese Yang Wang Hauptstr. 29 Bern 3012 Switz

erlan
d
15 Comércio Mineiro Pedro Afonso Av. dos Lusíadas, 23 São 05432-043 Brazil
Paulo
16 Consolidated Elizabeth Berkeley Gardens 12 London WX1 6LT UK

Holdings Brown Brewery
17 Drachenblut Sven Ottlieb Walserweg 21 Aachen 52066 Germ

Delikatessend any
18 Du monde entier Janine 67, rue des Cinquante Nantes 44000 Franc
Labrune Otages e
19 Eastern Connection Ann Devon 35 King George London WX3 6FW UK

20 Ernst Handel Roland Kirchgasse 6 Graz 8010 Austr
Mendel ia
21 Familia Arquibaldo Aria Cruz Rua Orós, 92 São 05442-030 Brazil

Paulo
22 FISSA Fabrica Inter. Diego Roel C/ Moralzarzal, 86 Madrid 28034 Spain

Salchichas S.A.
23 Folies gourmandes Martine 184, chaussée de Lille 59000 Franc

Rancé Tournai e
24 Folk och fä HB Maria Larsson Åkergatan 24 Bräcke S-844 67 Swed

en
25 Frankenversand Peter Franken Berliner Platz 43 Münche 80805 Germ

n any
26 France restauration Carine 54, rue Royale Nantes 44000 Franc

Schmitt e
27 Franchi S.p.A. Paolo Accorti Via Monte Bianco 34 Torino 10100 Italy
28 Furia Bacalhau e Lino Jardim das rosas n. 32 Lisboa 1675 Portu

Frutos do Mar Rodriguez gal
29 Galería del Eduardo Rambla de Cataluña, 23 Barcelo 08022 Spain
gastrónomo Saavedra na
30 Godos Cocina Típica José Pedro C/ Romero, 33 Sevilla 41101 Spain

Freyre
31 Gourmet André Av. Brasil, 442 Campin 04876-786 Brazil

Lanchonetes Fonseca as
32 Great Lakes Food Howard 2732 Baker Blvd. Eugene 97403 USA
Market Snyder
33 GROSELLA- Manuel 5ª Ave. Los Palos Caracas 1081 Vene

Restaurante Pereira Grandes zuela
34 Hanari Carnes Mario Pontes Rua do Paço, 67 Rio de 05454-876 Brazil

Janeiro
35 HILARIÓN-Abastos Carlos Carrera 22 con Ave. San 5022 Vene

Hernández Carlos Soublette #8-35 Cristób zuela
al
36 Hungry Coyote Yoshi Latimer City Center Plaza 516 Elgin 97827 USA
Import Store Main St.
37 Hungry Owl All- Patricia 8 Johnstown Road Cork Irela

Night Grocers McKenna nd
38 Island Trading Helen Bennett Garden House Crowther Cowes PO31 7PJ UK
Way
39 Königlich Essen Philip Cramer Maubelstr. 90 Brande 14776 Germ

nburg any
40 La corne Daniel Tonini 67, avenue de l'Europe Versaill 78000 Franc

d'abondance es e
41 La maison d'Asie Annette 1 rue Alsace-Lorraine Toulous 31000 Franc

Roulet e e
42 Laughing Bacchus Yoshi 1900 Oak St. Vancou V3F 2K1 Cana
Wine Cellars Tannamuri ver da
43 Lazy K Kountry John Steel 12 Orchestra Terrace Walla 99362 USA

Store Walla
44 Lehmanns Renate Magazinweg 7 Frankfu 60528 Germ

Marktstand Messner rt a.M. any
45 Let's Stop N Shop Jaime Yorres 87 Polk St. Suite 5 San 94117 USA
Francisc
o
46 LILA-Supermercado Carlos Carrera 52 con Ave. Barquisi 3508 Vene
González Bolívar #65-98 Llano meto zuela
Largo
47 LINO-Delicateses Felipe Ave. 5 de Mayo I. de 4980 Vene

Izquierdo Porlamar Margari zuela
ta
48 Lonesome Pine Fran Wilson 89 Chiaroscuro Rd. Portlan 97219 USA

Restaurant d
49 Magazzini Giovanni Via Ludovico il Moro 22 Bergam 24100 Italy

Alimentari Riuniti Rovelli o
50 Maison Dewey Catherine Rue Joseph-Bens 532 Bruxelle B-1180 Belgi

Dewey s um
51 Mère Paillarde Jean Fresnière 43 rue St. Laurent Montré H1J 1C3 Cana
al da
52 Morgenstern Alexander Heerstr. 22 Leipzig 04179 Germ

Gesundkost Feuer any
53 North/South Simon South House 300 London SW7 1RZ UK

Crowther Queensbridge
54 Océano Atlántico Yvonne Ing. Gustavo Moncada Buenos 1010 Arge

Ltda. Moncada 8585 Piso 20-A Aires ntina
55 Old World Rene Phillips 2743 Bering St. Anchor 99508 USA
Delicatessen age
56 Ottilies Käseladen Henriette Mehrheimerstr. 369 Köln 50739 Germ

Pfalzheim any
57 Paris spécialités Marie 265, boulevard Paris 75012 Franc

Bertrand Charonne e
58 Pericles Comidas Guillermo Calle Dr. Jorge Cash 321 México 05033 Mexi
clásicas Fernández D.F. co
59 Piccolo und mehr Georg Pipps Geislweg 14 Salzbur 5020 Austr

g ia
60 Princesa Isabel Isabel de Estrada da saúde n. 58 Lisboa 1756 Portu

Vinhoss Castro gal
61 Que Delícia Bernardo Rua da Panificadora, 12 Rio de 02389-673 Brazil

Batista Janeiro
62 Queen Cozinha Lúcia Alameda dos Canàrios, São 05487-020 Brazil

Carvalho 891 Paulo
63 QUICK-Stop Horst Kloss Taucherstraße 10 Cunewa 01307 Germ
lde any
64 Rancho grande Sergio Av. del Libertador 900 Buenos 1010 Arge
Gutiérrez Aires ntina
65 Rattlesnake Canyon Paula Wilson 2817 Milton Dr. Albuqu 87110 USA
Grocery erque
66 Reggiani Caseifici Maurizio Strada Provinciale 124 Reggio 42100 Italy

Moroni Emilia
67 Ricardo Adocicados Janete Av. Copacabana, 267 Rio de 02389-890 Brazil

Limeira Janeiro
68 Richter Supermarkt Michael Holz Grenzacherweg 237 Genève 1203 Switz

erlan
d
69 Romero y tomillo Alejandra Gran Vía, 1 Madrid 28001 Spain

Camino
70 Santé Gourmet Jonas Erling Skakkes gate 78 Stavern 4110 Norw

Bergulfsen ay
71 Save-a-lot Markets Jose Pavarotti 187 Suffolk Ln. Boise 83720 USA
72 Seven Seas Imports Hari Kumar 90 Wadhurst Rd. London OX15 4NB UK
73 Simons bistro Jytte Petersen Vinbæltet 34 Københ 1734 Den

avn mark
74 Spécialités du Dominique 25, rue Lauriston Paris 75016 Franc

monde Perrier e
75 Split Rail Beer & Ale Art P.O. Box 555 Lander 82520 USA
Braunschweig
er
76 Suprêmes délices Pascale Boulevard Tirou, 255 Charler B-6000 Belgi

Cartrain oi um
77 The Big Cheese Liz Nixon 89 Jefferson Way Suite 2 Portlan 97201 USA
d
78 The Cracker Box Liu Wong 55 Grizzly Peak Rd. Butte 59801 USA
79 Toms Spezialitäten Karin Josephs Luisenstr. 48 Münste 44087 Germ

r any
80 Tortuga Miguel Angel Avda. Azteca 123 México 05033 Mexi

Restaurante Paolino D.F. co
81 Tradição Anabela Av. Inês de Castro, 414 São 05634-030 Brazil
Hipermercados Domingues Paulo
82 Trail's Head Helvetius 722 DaVinci Blvd. Kirkland 98034 USA

Gourmet Nagy
Provisioners
83 Vaffeljernet Palle Ibsen Smagsløget 45 Århus 8200 Den

mark
84 Victuailles en stock Mary Saveley 2, rue du Commerce Lyon 69004 Franc

e
85 Vins et alcools Paul Henriot 59 rue de l'Abbaye Reims 51100 Franc

Chevalier e
86 Die Wandernde Kuh Rita Müller Adenauerallee 900 Stuttgar 70563 Germ
t any
87 Wartian Herkku Pirkko Torikatu 38 Oulu 90110 Finla

Koskitalo nd
88 Wellington Paula Parente Rua do Mercado, 12 Resend 08737-363 Brazil

Importadora e
89 White Clover Karl Jablonski 305 - 14th Ave. S. Suite Seattle 98128 USA
Markets 3B
90 Wilman Kala Matti Keskuskatu 45 Helsinki 21240 Finla

Karttunen nd
91 Wolski Zbyszek ul. Filtrowa 68 Walla 01-012 Pola

nd
IN Operator Examples
The following SQL statement selects all customers that are located in
"Germany", "France" or "UK":
Example
WHERE Country IN ('Germany', 'France', 'UK');
Try it Yourself »
The following SQL statement selects all customers that are NOT located in
"Germany", "France" or "UK":
Example
WHERE Country NOT IN ('Germany', 'France', 'UK');
Try it Yourself »
The following SQL statement selects all customers that are from the same
countries as the suppliers:
Example
WHERE Country IN (SELECT Country FROM Suppliers);
SQL BETWEEN Operator
The SQL BETWEEN Operator
The BETWEEN operator selects values within a given range. The values can be
numbers, text, or dates.
The BETWEEN operator is inclusive: begin and end values are included.
BETWEEN Syntax
FROM table_name
WHERE column_name BETWEEN value1 AND value2;
Demo Database
database:
BETWEEN Example
The following SQL statement selects all products with a price between 10 and
20:
Example
SELECT * FROM Products
WHERE Price BETWEEN 10 AND 20;
Try it Yourself »
NOT BETWEEN Example

To display the products outside the range of the previous example, use NOT
BETWEEN:
Example
WHERE Price NOT BETWEEN 10 AND 20;
Try it Yourself »
BETWEEN with IN Example

The following SQL statement selects all products with a price between 10 and
20. In addition; do not show products with a CategoryID of 1,2, or 3:
Example
WHERE Price BETWEEN 10 AND 20
AND CategoryID NOT IN (1,2,3);
Try it Yourself »
BETWEEN Text Values Example

The following SQL statement selects all products with a ProductName between
Carnarvon Tigers and Mozzarella di Giovanni:
Example
WHERE ProductName BETWEEN 'Carnarvon Tigers' AND 'Mozzarella di Giovanni'
ORDER BY ProductName;
Try it Yourself »
The following SQL statement selects all products with a ProductName between
Carnarvon Tigers and Chef Anton's Cajun Seasoning:
Example
WHERE ProductName BETWEEN "Carnarvon Tigers" AND "Chef Anton's Cajun
Seasoning"
Try it Yourself »
NOT BETWEEN Text Values Example
The following SQL statement selects all products with a ProductName not
between Carnarvon Tigers and Mozzarella di Giovanni:
Example
WHERE ProductName NOT BETWEEN 'Carnarvon Tigers' AND 'Mozzarella di
Giovanni'
Try it Yourself »
Sample Table
Below is a selection from the "Orders" table in the Northwind sample database:
OrderID CustomerID EmployeeID OrderDate ShipperID

10248 90 5 7/4/1996 3
10249 81 6 7/5/1996 1
10250 34 4 7/8/1996 2
10251 84 3 7/9/1996 1
10252 76 4 7/10/1996 2
BETWEEN Dates Example

The following SQL statement selects all orders with an OrderDate between '01-
July-1996' and '31-July-1996':
Example
SELECT * FROM Orders
WHERE OrderDate BETWEEN #07/01/1996# AND #07/31/1996#;
Try it Yourself »
OR:
Example
SELECT * FROM Orders
WHERE OrderDate BETWEEN '1996-07-01' AND '1996-07-31';
Try it Yourself »
SQL Aliases
SQL Aliases
SQL aliases are used to give a table, or a column in a table, a temporary name.
Aliases are often used to make column names more readable.
An alias only exists for the duration of that query.
An alias is created with the AS keyword.
Alias Column Syntax

SELECT column_name AS alias_name
FROM table_name;
Alias Table Syntax

FROM table_name AS alias_name;
Demo Database
In this tutorial we will use the well-known Northwind sample database.

helados

And a selection from the "Orders" table:
10354 58 8 1996-11-14 3
10355 4 6 1996-11-15 1
10356 86 6 1996-11-18 2
Alias for Columns Examples

The following SQL statement creates two aliases, one for the CustomerID
column and one for the CustomerName column:
Example
SELECT CustomerID AS ID, CustomerName AS Customer
FROM Customers;
Try it Yourself »
The following SQL statement creates two aliases, one for the CustomerName
column and one for the ContactName column. Note: It requires double
quotation marks or square brackets if the alias name contains spaces:
Example
SELECT CustomerName AS Customer, ContactName AS [Contact Person]
FROM Customers;
Try it Yourself »
The following SQL statement creates an alias named "Address" that combine
four columns (Address, PostalCode, City and Country):
Example
SELECT CustomerName, Address + ', ' + PostalCode + ' ' + City + ', ' +
Country AS Address
FROM Customers;
Try it Yourself »
Note: To get the SQL statement above to work in MySQL use the following:
SELECT CustomerName, CONCAT(Address,', ',PostalCode,', ',City,',

',Country) AS Address
FROM Customers;
Alias for Tables Example

The following SQL statement selects all the orders from the customer with
CustomerID=4 (Around the Horn). We use the "Customers" and "Orders"
tables, and give them the table aliases of "c" and "o" respectively (Here we use
aliases to make the SQL shorter):
Example
SELECT o.OrderID, o.OrderDate, c.CustomerName
FROM Customers AS c, Orders AS o
WHERE c.CustomerName='Around the Horn' AND c.CustomerID=o.CustomerID;
Try it Yourself »
The following SQL statement is the same as above, but without aliases:
Example
SELECT Orders.OrderID, Orders.OrderDate, Customers.CustomerName
FROM Customers, Orders
WHERE Customers.CustomerName='Around the
Horn' AND Customers.CustomerID=Orders.CustomerID;
Try it Yourself »
Aliases can be useful when:
 There are more than one table involved in a query

 Functions are used in the query
 Column names are big or not very readable
 Two or more columns are combined together
SQL Joins
SQL JOIN
A JOIN clause is used to combine rows from two or more tables, based on a
related column between them.
Let's look at a selection from the "Orders" table:
OrderID CustomerID OrderDate
10308 2 1996-09-18
10309 37 1996-09-19
10310 77 1996-09-20
Then, look at a selection from the "Customers" table:
CustomerID CustomerName ContactName Country
1 Alfreds Futterkiste Maria Anders Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Mexico
3 Antonio Moreno Taquería Antonio Moreno Mexico
Notice that the "CustomerID" column in the "Orders" table refers to the
"CustomerID" in the "Customers" table. The relationship between the two tables
above is the "CustomerID" column.
Then, we can create the following SQL statement (that contains an INNER JOIN),
that selects records that have matching values in both tables:
Example
SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers ON Orders.CustomerID=Customers.CustomerID;
Try it Yourself »
and it will produce something like this:
OrderID CustomerName OrderDate
10308 Ana Trujillo Emparedados y helados 9/18/1996
10365 Antonio Moreno Taquería 11/27/1996
10383 Around the Horn 12/16/1996
10355 Around the Horn 11/15/1996
10278 Berglunds snabbköp 8/12/1996

Different Types of SQL JOINs
Here are the different types of the JOINs in SQL:
 (INNER) JOIN: Returns records that have matching values in both tables
 LEFT (OUTER) JOIN: Returns all records from the left table, and the
matched records from the right table
 RIGHT (OUTER) JOIN: Returns all records from the right table, and the
matched records from the left table
 FULL (OUTER) JOIN: Returns all records when there is a match in either
left or right table

SQL INNER JOIN Keyword
SQL INNER JOIN Keyword
The INNER JOIN keyword selects records that have matching values in both
tables.
INNER JOIN Syntax
FROM table1
INNER JOIN table2
ON table1.column_name = table2.column_name;
Demo Database
Below is a selection from the "Orders" table:
10308 2 7 1996-09-18 3
10309 37 3 1996-09-19 1
10310 77 8 1996-09-20 2
And a selection from the "Customers" table:


helados 2222
3 Antonio Moreno Antonio Mataderos México 05023 Mexico

Taquería Moreno 2312 D.F.
SQL INNER JOIN Example

The following SQL statement selects all orders with customer information:
Example
SELECT Orders.OrderID, Customers.CustomerName
FROM Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID;
Try it Yourself »
Note: The INNER JOIN keyword selects all rows from both tables as long as there
is a match between the columns. If there are records in the "Orders" table that
do not have matches in "Customers", these orders will not be shown!
JOIN Three Tables

The following SQL statement selects all orders with customer and shipper
information:
Example
SELECT Orders.OrderID, Customers.CustomerName, Shippers.ShipperName
FROM ((Orders
INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID)
INNER JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID);
SQL LEFT JOIN Keyword
SQL LEFT JOIN Keyword
The LEFT JOIN keyword returns all records from the left table (table1), and the
matching records from the right table (table2). The result is 0 records from the
right side, if there is no match.
LEFT JOIN Syntax

FROM table1
LEFT JOIN table2
Note: In some databases LEFT JOIN is called LEFT OUTER JOIN.

Demo Database

helados 2222


10308 2 7 1996-09-18 3
10309 37 3 1996-09-19 1
10310 77 8 1996-09-20 2
SQL LEFT JOIN Example

The following SQL statement will select all customers, and any orders they
might have:
Example
SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;
Try it Yourself »
Note: The LEFT JOIN keyword returns all records from the left table (Customers),
even if there are no matches in the right table (Orders).
SQL RIGHT JOIN Keyword
SQL RIGHT JOIN Keyword
The RIGHT JOIN keyword returns all records from the right table (table2), and the
matching records from the left table (table1). The result is 0 records from the
left side, if there is no match.
RIGHT JOIN Syntax

FROM table1
RIGHT JOIN table2
Note: In some databases RIGHT JOIN is called RIGHT OUTER JOIN.
Demo Database
Below is a selection from the "Orders" table:

10308 2 7 1996-09-18 3
10309 37 3 1996-09-19 1
10310 77 8 1996-09-20 2
And a selection from the "Employees" table:
EmployeeID LastName FirstName BirthDate Photo
1 Davolio Nancy 12/8/1968 EmpID1.pic
2 Fuller Andrew 2/19/1952 EmpID2.pic
3 Leverling Janet 8/30/1963 EmpID3.pic
SQL RIGHT JOIN Example

The following SQL statement will return all employees, and any orders they
might have placed:
Example
SELECT Orders.OrderID, Employees.LastName, Employees.FirstName
FROM Orders
RIGHT JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
ORDER BY Orders.OrderID;
Try it Yourself »
Note: The RIGHT JOIN keyword returns all records from the right table

(Employees), even if there are no matches in the left table (Orders).
SQL FULL OUTER JOIN Keyword

SQL FULL OUTER JOIN Keyword
The FULL OUTER JOIN keyword returns all records when there is a match in left
(table1) or right (table2) table records.
Tip: FULL OUTER JOIN and FULL JOIN are the same.
FULL OUTER JOIN Syntax

FROM table1
FULL OUTER JOIN table2
ON table1.column_name = table2.column_name
WHERE condition;
Note: FULL OUTER JOIN can potentially return very large result-sets!
Demo Database

e

helados 2222


10308 2 7 1996-09-18 3
10309 37 3 1996-09-19 1
10310 77 8 1996-09-20 2
SQL FULL OUTER JOIN Example

The following SQL statement selects all customers, and all orders:
FROM Customers
FULL OUTER JOIN Orders ON Customers.CustomerID=Orders.CustomerID
ORDER BY Customers.CustomerName;
A selection from the result set may look like this:
CustomerName OrderID
Alfreds Futterkiste Null
Ana Trujillo Emparedados y helados 10308
Antonio Moreno Taquería Null

Note: The FULL OUTER JOIN keyword returns all matching records from both tables
whether the other table matches or not. So, if there are rows in "Customers"
that do not have matches in "Orders", or if there are rows in "Orders" that do
not have matches in "Customers", those rows will be listed as well.
SQL Self Join
SQL Self Join
A self join is a regular join, but the table is joined with itself.
Self Join Syntax

FROM table1 T1, table1 T2
WHERE condition;
T1 and T2 are different table aliases for the same table.
Demo Database

e

helados 2222

SQL Self Join Example

The following SQL statement matches customers that are from the same city:
Example
SELECT A.CustomerName AS CustomerName1,
B.CustomerName AS CustomerName2, A.City
FROM Customers A, Customers B
WHERE A.CustomerID <> B.CustomerID
AND A.City = B.City
ORDER BY A.City;
SQL UNION Operator
The SQL UNION Operator
The UNION operator is used to combine the result-set of two or
more SELECT statements.
 Every SELECT statement within UNION must have the same number of

columns
 The columns must also have similar data types
 The columns in every SELECT statement must also be in the same order
UNION Syntax
SELECT column_name(s) FROM table1
UNION
SELECT column_name(s) FROM table2;
UNION ALL Syntax

The UNION operator selects only distinct values by default. To allow duplicate
values, use UNION ALL:
SELECT column_name(s) FROM table1
UNION ALL
SELECT column_name(s) FROM table2;
Note: The column names in the result-set are usually equal to the column
names in the first SELECT statement.
Demo Database


helados 2222

And a selection from the "Suppliers" table:
SupplierID SupplierName ContactName Address City PostalCode Country
1 Exotic Liquid Charlotte 49 Gilbert London EC1 4SD UK

Cooper St.
2 New Orleans Cajun Shelley Burke P.O. Box New 70117 USA
Delights 78934 Orleans
3 Grandma Kelly's Regina Murphy 707 Oxford Ann Arbor 48104 USA
Homestead Rd.
SQL UNION Example

The following SQL statement returns the cities (only distinct values) from both
the "Customers" and the "Suppliers" table:
Example
SELECT City FROM Customers
UNION
SELECT City FROM Suppliers
ORDER BY City;
Try it Yourself »
Note: If some customers or suppliers have the same city, each city will only be
listed once, because UNION selects only distinct values. Use UNION ALL to also
select duplicate values!
SQL UNION ALL Example

The following SQL statement returns the cities (duplicate values also) from both
the "Customers" and the "Suppliers" table:
Example
SELECT City FROM Customers
UNION ALL
SELECT City FROM Suppliers
ORDER BY City;
Try it Yourself »
SQL UNION With WHERE

The following SQL statement returns the German cities (only distinct values)
from both the "Customers" and the "Suppliers" table:
Example
SELECT City, Country FROM Customers
UNION
SELECT City, Country FROM Suppliers
ORDER BY City;
Try it Yourself »
SQL UNION ALL With WHERE

The following SQL statement returns the German cities (duplicate values also)
from both the "Customers" and the "Suppliers" table:
Example
SELECT City, Country FROM Customers
UNION ALL
SELECT City, Country FROM Suppliers
ORDER BY City;
Try it Yourself »
Another UNION Example

The following SQL statement lists all customers and suppliers:
Example
SELECT 'Customer' AS Type, ContactName, City, Country
FROM Customers
UNION
SELECT 'Supplier', ContactName, City, Country
FROM Suppliers;
Try it Yourself »
Notice the "AS Type" above - it is an alias. SQL Aliases are used to give a table
or a column a temporary name. An alias only exists for the duration of the
query. So, here we have created a temporary column named "Type", that list
whether the contact person is a "Customer" or a "Supplier".
SQL GROUP BY Statement
The SQL GROUP BY Statement
The GROUP BY statement groups rows that have the same values into summary
rows, like "find the number of customers in each country".
The GROUP BY statement is often used with aggregate functions

(COUNT(), MAX(), MIN(), SUM(), AVG()) to group the result-set by one or more
columns.
GROUP BY Syntax
FROM table_name
WHERE condition
GROUP BY column_name(s)
ORDER BY column_name(s);
Demo Database
database:

helados 2222


Berglund
SQL GROUP BY Examples

The following SQL statement lists the number of customers in each country:
Example
SELECT COUNT(CustomerID), Country
FROM Customers
GROUP BY Country;
Try it Yourself »
The following SQL statement lists the number of customers in each country,
sorted high to low:
Example
FROM Customers
GROUP BY Country
ORDER BY COUNT(CustomerID) DESC;
Try it Yourself »
Demo Database
10248 90 5 1996-07-04 3
10249 81 6 1996-07-05 1
10250 34 4 1996-07-08 2
And a selection from the "Shippers" table:
ShipperID ShipperName
1 Speedy Express
2 United Package
3 Federal Shipping
GROUP BY With JOIN Example

The following SQL statement lists the number of orders sent by each shipper:
Example
SELECT Shippers.ShipperName, COUNT(Orders.OrderID) AS NumberOfOrders FROM
Orders
LEFT JOIN Shippers ON Orders.ShipperID = Shippers.ShipperID
GROUP BY ShipperName;
Try it Yourself »
SQL HAVING Clause
The SQL HAVING Clause
The HAVING clause was added to SQL because the WHERE keyword cannot be used
with aggregate functions.
HAVING Syntax
FROM table_name
WHERE condition
GROUP BY column_name(s)
HAVING condition
ORDER BY column_name(s);
Demo Database
database:

D

helados

Berglund
SQL HAVING Examples

The following SQL statement lists the number of customers in each country.
Only include countries with more than 5 customers:
Example
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5;
Try it Yourself »
The following SQL statement lists the number of customers in each country,
sorted high to low (Only include countries with more than 5 customers):
Example
FROM Customers
GROUP BY Country
HAVING COUNT(CustomerID) > 5
ORDER BY COUNT(CustomerID) DESC;
Try it Yourself »
Demo Database
10248 90 5 1996-07-04 3
10249 81 6 1996-07-05 1
10250 34 4 1996-07-08 2
And a selection from the "Employees" table:

EmployeeID LastName FirstName BirthDate Photo Notes
1 Davolio Nancy 1968-12-08 EmpID1.pic Education includes a BA....
2 Fuller Andrew 1952-02-19 EmpID2.pic Andrew received his BTS....
3 Leverling Janet 1963-08-30 EmpID3.pic Janet has a BS degree....
More HAVING Examples

The following SQL statement lists the employees that have registered more than
10 orders:
Example
SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders
FROM (Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID)
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 10;
Try it Yourself »
The following SQL statement lists if the employees "Davolio" or "Fuller" have
registered more than 25 orders:
Example
SELECT Employees.LastName, COUNT(Orders.OrderID) AS NumberOfOrders
FROM Orders
INNER JOIN Employees ON Orders.EmployeeID = Employees.EmployeeID
WHERE LastName = 'Davolio' OR LastName = 'Fuller'
GROUP BY LastName
HAVING COUNT(Orders.OrderID) > 25;
Try it Yourself »
SQL EXISTS Operator
The SQL EXISTS Operator
The EXISTS operator is used to test for the existence of any record in a subquery.
The EXISTS operator returns TRUE if the subquery returns one or more records.
EXISTS Syntax
FROM table_name
WHERE EXISTS
(SELECT column_name FROM table_name WHERE condition);
Demo Database
database:
SupplierID SupplierName ContactName Address City PostalCod Country

e
1 Exotic Liquid Charlotte 49 Gilbert St. London EC1 4SD UK

Cooper
2 New Orleans Cajun Shelley Burke P.O. Box 78934 New 70117 USA
Delights Orleans
3 Grandma Kelly's Regina Murphy 707 Oxford Rd. Ann Arbor 48104 USA
Homestead
4 Tokyo Traders Yoshi Nagase 9-8 Sekimai Tokyo 100 Japan

Musashino-shi
SQL EXISTS Examples

The following SQL statement returns TRUE and lists the suppliers with a product
price less than 20:
Example
SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID
= Suppliers.supplierID AND Price < 20);
Try it Yourself »
The following SQL statement returns TRUE and lists the suppliers with a product
price equal to 22:
Example
SELECT SupplierName
FROM Suppliers
WHERE EXISTS (SELECT ProductName FROM Products WHERE Products.SupplierID
= Suppliers.supplierID AND Price = 22);
SQL ANY and ALL Operators

The SQL ANY and ALL Operators
The ANY and ALL operators allow you to perform a comparison between a single
column value and a range of other values.
The SQL ANY Operator

The ANY operator:
 returns a boolean value as a result

 returns TRUE if ANY of the subquery values meet the condition
ANY means that the condition will be true if the operation is true for any of the
values in the range.
ANY Syntax
FROM table_name
WHERE column_name operator ANY
(SELECT column_name
FROM table_name
WHERE condition);
Note: The operator must be a standard comparison operator (=, <>, !=, >,

>=, <, or <=).
The SQL ALL Operator

The ALL operator:
 returns a boolean value as a result

 returns TRUE if ALL of the subquery values meet the condition
 is used with SELECT, WHERE and HAVING statements
ALL means that the condition will be true only if the operation is true for all
values in the range.
ALL Syntax With SELECT

SELECT ALL column_name(s)
FROM table_name
WHERE condition;
ALL Syntax With WHERE or HAVING

FROM table_name
WHERE column_name operator ALL
(SELECT column_name
FROM table_name
WHERE condition);
Note: The operator must be a standard comparison operator (=, <>, !=, >,

>=, <, or <=).
Demo Database
database:
6 Grandma's Boysenberry Spread 3 2 12 - 8 oz jars 25
7 Uncle Bob's Organic Dried Pears 3 7 12 - 1 lb pkgs. 30
8 Northwoods Cranberry Sauce 3 2 12 - 12 oz jars 40
9 Mishi Kobe Niku 4 6 18 - 500 g pkgs. 97

And a selection from the "OrderDetails" table:
1 10248 11 12
2 10248 42 10
3 10248 72 5
4 10249 14 9
5 10249 51 40
6 10250 41 10
7 10250 51 35
8 10250 65 15
9 10251 22 6
10 10251 57 15
SQL ANY Examples

The following SQL statement lists the ProductName if it finds ANY records in the
OrderDetails table has Quantity equal to 10 (this will return TRUE because the
Quantity column has some values of 10):
Example
SELECT ProductName
FROM Products
WHERE ProductID = ANY
(SELECT ProductID
FROM OrderDetails
WHERE Quantity = 10);
Try it Yourself »
OrderDetails table has Quantity larger than 99 (this will return TRUE because
the Quantity column has some values larger than 99):
Example
SELECT ProductName
FROM Products
(SELECT ProductID
FROM OrderDetails
WHERE Quantity > 99);
Try it Yourself »
OrderDetails table has Quantity larger than 1000 (this will return FALSE
because the Quantity column has no values larger than 1000):
Example
SELECT ProductName
FROM Products
(SELECT ProductID
FROM OrderDetails
WHERE Quantity > 1000);
Try it Yourself »
SQL ALL Examples

The following SQL statement lists ALL the product names:
Example
SELECT ALL ProductName
FROM Products
WHERE TRUE;
Try it Yourself »
The following SQL statement lists the ProductName if ALL the records in the
OrderDetails table has Quantity equal to 10. This will of course return FALSE
because the Quantity column has many different values (not only the value of
10):
Example
SELECT ProductName
FROM Products
WHERE ProductID = ALL
(SELECT ProductID
FROM OrderDetails
WHERE Quantity = 10);
Try it Yourself »
SQL SELECT INTO Statement
The SQL SELECT INTO Statement
The SELECT INTO statement copies data from one table into a new table.
SELECT INTO Syntax

Copy all columns into a new table:
SELECT *
INTO newtable [IN externaldb]
FROM oldtable
WHERE condition;
Copy only some columns into a new table:
SELECT column1, column2, column3, ...
INTO newtable [IN externaldb]
FROM oldtable
WHERE condition;
The new table will be created with the column-names and types as defined in
the old table. You can create new column names using the AS clause.
SQL SELECT INTO Examples

The following SQL statement creates a backup copy of Customers:
SELECT * INTO CustomersBackup2017
FROM Customers;
The following SQL statement uses the IN clause to copy the table into a new
table in another database:
SELECT * INTO CustomersBackup2017 IN 'Backup.mdb'
FROM Customers;
The following SQL statement copies only a few columns into a new table:
SELECT CustomerName, ContactName INTO CustomersBackup2017
FROM Customers;
The following SQL statement copies only the German customers into a new
table:
SELECT * INTO CustomersGermany
FROM Customers
WHERE Country = 'Germany';
The following SQL statement copies data from more than one table into a new
table:
INTO CustomersOrderBackup2017
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID;
Tip: SELECT INTO can also be used to create a new, empty table using the schema
of another. Just add a WHERE clause that causes the query to return no data:
SELECT * INTO newtable
FROM oldtable
WHERE 1 = 0;
SQL INSERT INTO
SELECT Statement
The SQL INSERT INTO SELECT Statement
The INSERT INTO SELECT statement copies data from one table and inserts it into
another table.
The INSERT INTO SELECT statement requires that the data types in source and
target tables matches.
Note: The existing records in the target table are unaffected.

INSERT INTO SELECT Syntax
Copy all columns from one table to another table:
INSERT INTO table2
SELECT * FROM table1
WHERE condition;
Copy only some columns from one table into another table:
INSERT INTO table2 (column1, column2, column3, ...)

SELECT column1, column2, column3, ...
FROM table1
WHERE condition;
Demo Database

e

helados 2222

SupplierID SupplierName ContactName Address City Postal Country

Code
1 Exotic Liquid Charlotte 49 Gilbert St. Londona EC1 4SD UK

Cooper
2 New Orleans Cajun Shelley Burke P.O. Box New 70117 USA
Delights 78934 Orleans
3 Grandma Kelly's Regina Murphy 707 Oxford Ann Arbor 48104 USA
Homestead Rd.
SQL INSERT INTO SELECT Examples

The following SQL statement copies "Suppliers" into "Customers" (the columns
that are not filled with data, will contain NULL):
Example
SELECT SupplierName, City, Country FROM Suppliers;
Try it Yourself »
The following SQL statement copies "Suppliers" into "Customers" (fill all
columns):
Example
INSERT INTO Customers (CustomerName, ContactName, Address, City,
PostalCode, Country)
SELECT SupplierName, ContactName, Address, City,
PostalCode, Country FROM Suppliers;
Try it Yourself »
The following SQL statement copies only the German suppliers into
"Customers":
Example
SELECT SupplierName, City, Country FROM Suppliers
WHERE Country='Germany';
Try it Yourself »
SQL CASE Statement
The SQL CASE Statement
The CASE statement goes through conditions and returns a value when the first
condition is met (like an if-then-else statement). So, once a condition is true, it
will stop reading and return the result. If no conditions are true, it returns the
value in the ELSE clause.
If there is no ELSE part and no conditions are true, it returns NULL.
CASE Syntax
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
ELSE result
END;
Demo Database
Below is a selection from the "OrderDetails" table in the Northwind sample
database:
1 10248 11 12
2 10248 42 10
3 10248 72 5
4 10249 14 9
5 10249 51 40
SQL CASE Examples
The following SQL goes through conditions and returns a value when the first
condition is met:
Example
SELECT OrderID, Quantity,
CASE
WHEN Quantity > 30 THEN 'The quantity is greater than 30'
WHEN Quantity = 30 THEN 'The quantity is 30'
ELSE 'The quantity is under 30'
END AS QuantityText
FROM OrderDetails;
Try it Yourself »
The following SQL will order the customers by City. However, if City is NULL,
then order by Country:
Example
SELECT CustomerName, City, Country
FROM Customers
ORDER BY
(CASE
WHEN City IS NULL THEN Country
ELSE City
END);
SQL NULL Functions
SQL IFNULL(), ISNULL(), COALESCE(), and
NVL() Functions
Look at the following "Products" table:
P_Id ProductName UnitPrice UnitsInStock UnitsOnOrder
1 Jarlsberg 10.45 16 15
2 Mascarpone 32.56 23
3 Gorgonzola 15.67 9 20
Suppose that the "UnitsOnOrder" column is optional, and may contain NULL
values.
Look at the following SELECT statement:

SELECT ProductName, UnitPrice * (UnitsInStock + UnitsOnOrder)
FROM Products;
In the example above, if any of the "UnitsOnOrder" values are NULL, the result
will be NULL.
Solutions
MySQL
The MySQL IFNULL() function lets you return an alternative value if an

expression is NULL:
SELECT ProductName, UnitPrice * (UnitsInStock + IFNULL(UnitsOnOrder, 0))

FROM Products;
or we can use the COALESCE() function, like this:
SELECT ProductName, UnitPrice * (UnitsInStock

+ COALESCE(UnitsOnOrder, 0))
FROM Products;
SQL Server
The SQL Server ISNULL() function lets you return an alternative value when an

expression is NULL:
SELECT ProductName, UnitPrice * (UnitsInStock + ISNULL(UnitsOnOrder, 0))

FROM Products;
MS Access
The MS Access IsNull() function returns TRUE (-1) if the expression is a null

value, otherwise FALSE (0):
SELECT ProductName, UnitPrice * (UnitsInStock +

IIF(IsNull(UnitsOnOrder), 0, UnitsOnOrder))
FROM Products;
Oracle
The Oracle NVL() function achieves the same result:
SELECT ProductName, UnitPrice * (UnitsInStock + NVL(UnitsOnOrder, 0))

FROM Products;
SQL Stored Procedures for SQL

Server
What is a Stored Procedure?
A stored procedure is a prepared SQL code that you can save, so the code can
be reused over and over again.
So if you have an SQL query that you write over and over again, save it as a
stored procedure, and then just call it to execute it.
You can also pass parameters to a stored procedure, so that the stored
procedure can act based on the parameter value(s) that is passed.
Stored Procedure Syntax

CREATE PROCEDURE procedure_name
AS
sql_statement
GO;
Execute a Stored Procedure

EXEC procedure_name;
Demo Database
database:

helados


Berglund
Stored Procedure Example

The following SQL statement creates a stored procedure named
"SelectAllCustomers" that selects all records from the "Customers" table:
Example
CREATE PROCEDURE SelectAllCustomers
AS
GO;
Execute the stored procedure above as follows:
Example
EXEC SelectAllCustomers;
Stored Procedure With One Parameter

The following SQL statement creates a stored procedure that selects Customers
from a particular City from the "Customers" table:
Example
CREATE PROCEDURE SelectAllCustomers @City nvarchar(30)
AS
SELECT * FROM Customers WHERE City = @City
GO;
Example
EXEC SelectAllCustomers @City = 'London';
Stored Procedure With Multiple

Parameters
Setting up multiple parameters is very easy. Just list each parameter and the
data type separated by a comma as shown below.
The following SQL statement creates a stored procedure that selects Customers
from a particular City with a particular PostalCode from the "Customers" table:
Example
CREATE PROCEDURE SelectAllCustomers @City nvarchar(30), @PostalCode
nvarchar(10)
AS
SELECT * FROM Customers WHERE City = @City AND PostalCode = @PostalCode
GO;
Example
EXEC SelectAllCustomers @City = 'London', @PostalCode = 'WA1 1DP';
SQL Comments
SQL Comments
Comments are used to explain sections of SQL statements, or to prevent
execution of SQL statements.
Note: The examples in this chapter will not work in Firefox and
Microsoft Edge!
Comments are not supported in Microsoft Access databases. Firefox and

Microsoft Edge are using Microsoft Access database in our examples.
Single Line Comments

Single line comments start with --.
Any text between -- and the end of the line will be ignored (will not be
executed).
The following example uses a single-line comment as an explanation:
Example
--Select all:
Try it Yourself »
The following example uses a single-line comment to ignore the end of a line:
Example
SELECT * FROM Customers -- WHERE City='Berlin';
Try it Yourself »
The following example uses a single-line comment to ignore a statement:

Example
--SELECT * FROM Customers;
SELECT * FROM Products;
Try it Yourself »
Multi-line Comments
Multi-line comments start with /* and end with */.
Any text between /* and */ will be ignored.
The following example uses a multi-line comment as an explanation:
Example
/*Select all the columns
of all the records
in the Customers table:*/
Try it Yourself »
The following example uses a multi-line comment to ignore many statements:
Example
/*SELECT * FROM Customers;
SELECT * FROM Products;
SELECT * FROM Orders;
SELECT * FROM Categories;*/
SELECT * FROM Suppliers;
Try it Yourself »
To ignore just a part of a statement, also use the /* */ comment.
The following example uses a comment to ignore part of a line:
Example
SELECT CustomerName, /*City,*/ Country FROM Customers;
Try it Yourself »
The following example uses a comment to ignore part of a statement:
Example
SELECT * FROM Customers WHERE (CustomerName LIKE 'L%'
OR CustomerName LIKE 'R%' /*OR CustomerName LIKE 'S%'
OR CustomerName LIKE 'T%'*/ OR CustomerName LIKE 'W%')
AND Country='USA'
ORDER BY CustomerName;
SQL Operators
SQL Arithmetic Operators
+ Add Try it
- Subtract Try it
* Multiply Try it
/ Divide Try it
% Modulo Try it
SQL Bitwise Operators
Operator Description
& Bitwise AND
| Bitwise OR
^ Bitwise exclusive OR
SQL Comparison Operators
= Equal to Try it
> Greater than Try it
< Less than Try it
>= Greater than or equal to Try it
<= Less than or equal to Try it
<> Not equal to Try it

SQL Compound Operators
Operator Description
+= Add equals
-= Subtract equals
*= Multiply equals
/= Divide equals
%= Modulo equals
&= Bitwise AND equals
^-= Bitwise exclusive equals
|*= Bitwise OR equals
SQL Logical Operators
ALL TRUE if all of the subquery values meet the condition Try it
AND TRUE if all the conditions separated by AND is TRUE Try it
ANY TRUE if any of the subquery values meet the condition Try it
BETWEEN TRUE if the operand is within the range of comparisons Try it
EXISTS TRUE if the subquery returns one or more records Try it
IN TRUE if the operand is equal to one of a list of expressions Try it
LIKE TRUE if the operand matches a pattern Try it
NOT Displays a record if the condition(s) is NOT TRUE Try it
OR TRUE if any of the conditions separated by OR is TRUE Try it
SOME TRUE if any of the subquery values meet the condition Try it
SQL CREATE
DATABASE Statement
The SQL CREATE DATABASE Statement
The CREATE DATABASE statement is used to create a new SQL database.
Syntax
CREATE DATABASE databasename;
CREATE DATABASE Example
The following SQL statement creates a database called "testDB":
Example
CREATE DATABASE testDB;
Tip: Make sure you have admin privilege before creating any database. Once a
database is created, you can check it in the list of databases with the following
SQL command: SHOW DATABASES;
SQL DROP DATABASE Statement
The SQL DROP DATABASE Statement
The DROP DATABASE statement is used to drop an existing SQL database.
Syntax
DROP DATABASE databasename;
Note: Be careful before dropping a database. Deleting a database will result in

loss of complete information stored in the database!
DROP DATABASE Example

The following SQL statement drops the existing database "testDB":
Example
DROP DATABASE testDB;
Tip: Make sure you have admin privilege before dropping any database. Once a
database is dropped, you can check it in the list of databases with the following
SQL command: SHOW DATABASES;
SQL BACKUP DATABASE for SQL
Server
The SQL BACKUP DATABASE Statement
The BACKUP DATABASE statement is used in SQL Server to create a full back up of
an existing SQL database.
Syntax
BACKUP DATABASE databasename
TO DISK = 'filepath';
The SQL BACKUP WITH DIFFERENTIAL

Statement
A differential back up only backs up the parts of the database that have
changed since the last full database backup.
Syntax
BACKUP DATABASE databasename
TO DISK = 'filepath'
WITH DIFFERENTIAL;
BACKUP DATABASE Example

The following SQL statement creates a full back up of the existing database
"testDB" to the D disk:
Example
BACKUP DATABASE testDB
TO DISK = 'D:\backups\testDB.bak';
Tip: Always back up the database to a different drive than the actual database.
Then, if you get a disk crash, you will not lose your backup file along with the
database.
BACKUP WITH DIFFERENTIAL Example

The following SQL statement creates a differential back up of the database
"testDB":
Example
BACKUP DATABASE testDB
TO DISK = 'D:\backups\testDB.bak'
WITH DIFFERENTIAL;
Tip: A differential back up reduces the back up time (since only the changes are
backed up).
SQL CREATE TABLE Statement
The SQL CREATE TABLE Statement
The CREATE TABLE statement is used to create a new table in a database.
Syntax
CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
....
);
The column parameters specify the names of the columns of the table.
The datatype parameter specifies the type of data the column can hold (e.g.
varchar, integer, date, etc.).
Tip: For an overview of the available data types, go to our complete Data Types

Reference.
SQL CREATE TABLE Example

The following example creates a table called "Persons" that contains five
columns: PersonID, LastName, FirstName, Address, and City:
Example
CREATE TABLE Persons (
PersonID int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255)
);
Try it Yourself »
The PersonID column is of type int and will hold an integer.
The LastName, FirstName, Address, and City columns are of type varchar and
will hold characters, and the maximum length for these fields is 255 characters.
The empty "Persons" table will now look like this:
PersonID LastName FirstName Address City

Tip: The empty "Persons" table can now be filled with data with the
SQL INSERT INTO statement.
Create Table Using Another Table

A copy of an existing table can also be created using CREATE TABLE.
The new table gets the same column definitions. All columns or specific columns
can be selected.
If you create a new table using an existing table, the new table will be filled
with the existing values from the old table.
Syntax
CREATE TABLE new_table_name AS
SELECT column1, column2,...
FROM existing_table_name
WHERE ....;
The following SQL creates a new table called "TestTables" (which is a copy of
the "Customers" table):
Example
CREATE TABLE TestTable AS
SELECT customername, contactname
FROM customers;
Try it Yourself »
SQL DROP TABLE Statement
The SQL DROP TABLE Statement
The DROP TABLE statement is used to drop an existing table in a database.
Syntax
DROP TABLE table_name;
Note: Be careful before dropping a table. Deleting a table will result in loss of
complete information stored in the table!
SQL DROP TABLE Example

The following SQL statement drops the existing table "Shippers":
Example
DROP TABLE Shippers;
Try it Yourself »
SQL TRUNCATE TABLE

The TRUNCATE TABLE statement is used to delete the data inside a table, but not
the table itself.
Syntax
TRUNCATE TABLE table_name;
SQL ALTER TABLE Statement
SQL ALTER TABLE Statement
The ALTER TABLE statement is used to add, delete, or modify columns in an
existing table.
The ALTER TABLE statement is also used to add and drop various constraints on an

existing table.
ALTER TABLE - ADD Column

To add a column in a table, use the following syntax:
ALTER TABLE table_name
ADD column_name datatype;
The following SQL adds an "Email" column to the "Customers" table:
Example
ALTER TABLE Customers
ADD Email varchar(255);
Try it Yourself »
ALTER TABLE - DROP COLUMN

To delete a column in a table, use the following syntax (notice that some
database systems don't allow deleting a column):
DROP COLUMN column_name;
The following SQL deletes the "Email" column from the "Customers" table:
Example
ALTER TABLE Customers
DROP COLUMN Email;
Try it Yourself »
ALTER TABLE - ALTER/MODIFY COLUMN

To change the data type of a column in a table, use the following syntax:
SQL Server / MS Access:
ALTER COLUMN column_name datatype;
My SQL / Oracle (prior version 10G):
MODIFY COLUMN column_name datatype;
Oracle 10G and later:
MODIFY column_name datatype;
SQL ALTER TABLE Example

Look at the "Persons" table:
ID LastName FirstName Address City

1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger
Now we want to add a column named "DateOfBirth" in the "Persons" table.
We use the following SQL statement:
ALTER TABLE Persons
ADD DateOfBirth date;
Notice that the new column, "DateOfBirth", is of type date and is going to hold a
date. The data type specifies what type of data the column can hold. For a
complete reference of all the data types available in MS Access, MySQL, and
SQL Server, go to our complete Data Types reference.
The "Persons" table will now look like this:
ID LastName FirstName Address City DateOfBirth

Change Data Type Example
Now we want to change the data type of the column named "DateOfBirth" in the
"Persons" table.
ALTER TABLE Persons
ALTER COLUMN DateOfBirth year;
Notice that the "DateOfBirth" column is now of type year and is going to hold a
year in a two- or four-digit format.
DROP COLUMN Example

Next, we want to delete the column named "DateOfBirth" in the "Persons" table.
ALTER TABLE Persons
DROP COLUMN DateOfBirth;
The "Persons" table will now look like this:
ID LastName FirstName Address City

SQL Constraints
SQL constraints are used to specify rules for data in a table.
SQL Create Constraints

Constraints can be specified when the table is created with the CREATE
TABLE statement, or after the table is created with the ALTER TABLE statement.
Syntax
CREATE TABLE table_name (
column1 datatype constraint,
....
);
SQL Constraints
SQL constraints are used to specify rules for the data in a table.
Constraints are used to limit the type of data that can go into a table. This
ensures the accuracy and reliability of the data in the table. If there is any
violation between the constraint and the data action, the action is aborted.
Constraints can be column level or table level. Column level constraints apply to
a column, and table level constraints apply to the whole table.
The following constraints are commonly used in SQL:
 NOT NULL - Ensures that a column cannot have a NULL value

 UNIQUE - Ensures that all values in a column are different
 PRIMARY KEY - A combination of a NOT NULL and UNIQUE. Uniquely identifies
each row in a table
 FOREIGN KEY - Prevents actions that would destroy links between tables
 CHECK - Ensures that the values in a column satisfies a specific condition
 DEFAULT - Sets a default value for a column if no value is specified
 CREATE INDEX - Used to create and retrieve data from the database very
quickly
SQL NOT NULL Constraint
SQL NOT NULL Constraint
By default, a column can hold NULL values.
The NOT NULL constraint enforces a column to NOT accept NULL values.
This enforces a field to always contain a value, which means that you cannot
insert a new record, or update a record without adding a value to this field.
SQL NOT NULL on CREATE TABLE

The following SQL ensures that the "ID", "LastName", and "FirstName" columns
will NOT accept NULL values when the "Persons" table is created:
Example
ID int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255) NOT NULL,
Age int
);
Try it Yourself »
SQL NOT NULL on ALTER TABLE
To create a NOT NULL constraint on the "Age" column when the "Persons" table is
already created, use the following SQL:
ALTER TABLE Persons
MODIFY Age int NOT NULL;
SQL UNIQUE Constraint
SQL UNIQUE Constraint
The UNIQUE constraint ensures that all values in a column are different.
Both the UNIQUE and PRIMARY KEY constraints provide a guarantee for uniqueness

for a column or set of columns.
A PRIMARY KEY constraint automatically has a UNIQUE constraint.
However, you can have many UNIQUE constraints per table, but only one PRIMARY
KEY constraint per table.
SQL UNIQUE Constraint on CREATE

TABLE
The following SQL creates a UNIQUE constraint on the "ID" column when the
"Persons" table is created:
SQL Server / Oracle / MS Access:
ID int NOT NULL UNIQUE,
Age int
);
MySQL:
ID int NOT NULL,
Age int,
UNIQUE (ID)
);
To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple

columns, use the following SQL syntax:
MySQL / SQL Server / Oracle / MS Access:
ID int NOT NULL,
Age int,
CONSTRAINT UC_Person UNIQUE (ID,LastName)
);
SQL UNIQUE Constraint on ALTER TABLE

To create a UNIQUE constraint on the "ID" column when the table is already
created, use the following SQL:
ALTER TABLE Persons
ADD UNIQUE (ID);
To name a UNIQUE constraint, and to define a UNIQUE constraint on multiple

columns, use the following SQL syntax:
ALTER TABLE Persons
ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);
DROP a UNIQUE Constraint
To drop a UNIQUE constraint, use the following SQL:
MySQL:
ALTER TABLE Persons
DROP INDEX UC_Person;
ALTER TABLE Persons
DROP CONSTRAINT UC_Person;
SQL PRIMARY KEY Constraint
SQL PRIMARY KEY Constraint
The PRIMARY KEY constraint uniquely identifies each record in a table.
Primary keys must contain UNIQUE values, and cannot contain NULL values.
A table can have only ONE primary key; and in the table, this primary key can
consist of single or multiple columns (fields).
SQL PRIMARY KEY on CREATE TABLE

The following SQL creates a PRIMARY KEY on the "ID" column when the "Persons"
table is created:
MySQL:
ID int NOT NULL,
Age int,
PRIMARY KEY (ID)
);
ID int NOT NULL PRIMARY KEY,
Age int
);
To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY

KEY constraint on multiple columns, use the following SQL syntax:
ID int NOT NULL,
Age int,
CONSTRAINT PK_Person PRIMARY KEY (ID,LastName)
);
Note: In the example above there is only ONE PRIMARY KEY (PK_Person).

However, the VALUE of the primary key is made up of TWO COLUMNS (ID +
LastName).
SQL PRIMARY KEY on ALTER TABLE

To create a PRIMARY KEY constraint on the "ID" column when the table is already
ALTER TABLE Persons
ADD PRIMARY KEY (ID);
To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY
ALTER TABLE Persons
ADD CONSTRAINT PK_Person PRIMARY KEY (ID,LastName);
Note: If you use ALTER TABLE to add a primary key, the primary key column(s)
must have been declared to not contain NULL values (when the table was first
created).
DROP a PRIMARY KEY Constraint

To drop a PRIMARY KEY constraint, use the following SQL:
MySQL:
ALTER TABLE Persons
DROP PRIMARY KEY;
ALTER TABLE Persons
DROP CONSTRAINT PK_Person;
SQL FOREIGN KEY Constraint
SQL FOREIGN KEY Constraint
The FOREIGN KEY constraint is used to prevent actions that would destroy links
between tables.
A FOREIGN KEY is a field (or collection of fields) in one table, that refers to
the PRIMARY KEY in another table.
The table with the foreign key is called the child table, and the table with the
primary key is called the referenced or parent table.
Look at the following two tables:
Persons Table
PersonID LastName FirstName Age
1 Hansen Ola 30
2 Svendson Tove 23
3 Pettersen Kari 20
Orders Table
OrderID OrderNumber PersonID
1 77895 3
2 44678 3
3 22456 2
4 24562 1
Notice that the "PersonID" column in the "Orders" table points to the "PersonID"
column in the "Persons" table.
The "PersonID" column in the "Persons" table is the PRIMARY KEY in the "Persons"
table.
The "PersonID" column in the "Orders" table is a FOREIGN KEY in the "Orders"
table.
The FOREIGN KEY constraint prevents invalid data from being inserted into the
foreign key column, because it has to be one of the values contained in the
parent table.
SQL FOREIGN KEY on CREATE TABLE

The following SQL creates a FOREIGN KEY on the "PersonID" column when the
"Orders" table is created:
MySQL:
CREATE TABLE Orders (
OrderID int NOT NULL,
OrderNumber int NOT NULL,
PersonID int,
PRIMARY KEY (OrderID),
FOREIGN KEY (PersonID) REFERENCES Persons(PersonID)
);
OrderID int NOT NULL PRIMARY KEY,
PersonID int FOREIGN KEY REFERENCES Persons(PersonID)
);
To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN

OrderID int NOT NULL,
PersonID int,
PRIMARY KEY (OrderID),
CONSTRAINT FK_PersonOrder FOREIGN KEY (PersonID)
REFERENCES Persons(PersonID)
);
SQL FOREIGN KEY on ALTER TABLE

To create a FOREIGN KEY constraint on the "PersonID" column when the "Orders"
table is already created, use the following SQL:
ALTER TABLE Orders
ADD FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);
To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN

ALTER TABLE Orders
ADD CONSTRAINT FK_PersonOrder
FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);
DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:
MySQL:
ALTER TABLE Orders
DROP FOREIGN KEY FK_PersonOrder;
ALTER TABLE Orders
DROP CONSTRAINT FK_PersonOrder;
SQL CHECK Constraint
SQL CHECK Constraint
The CHECK constraint is used to limit the value range that can be placed in a
column.
If you define a CHECK constraint on a column it will allow only certain values for
this column.
If you define a CHECK constraint on a table it can limit the values in certain

columns based on values in other columns in the row.
SQL CHECK on CREATE TABLE

The following SQL creates a CHECK constraint on the "Age" column when the
"Persons" table is created. The CHECK constraint ensures that the age of a person
must be 18, or older:
MySQL:
ID int NOT NULL,
Age int,
CHECK (Age>=18)
);

ID int NOT NULL,
Age int CHECK (Age>=18)
);
To allow naming of a CHECK constraint, and for defining a CHECK constraint on

multiple columns, use the following SQL syntax:
ID int NOT NULL,
Age int,
City varchar(255),
CONSTRAINT CHK_Person CHECK (Age>=18 AND City='Sandnes')
);
SQL CHECK on ALTER TABLE

To create a CHECK constraint on the "Age" column when the table is already
ALTER TABLE Persons
ADD CHECK (Age>=18);
To allow naming of a CHECK constraint, and for defining a CHECK constraint on

multiple columns, use the following SQL syntax:
ALTER TABLE Persons
ADD CONSTRAINT CHK_PersonAge CHECK (Age>=18 AND City='Sandnes');
DROP a CHECK Constraint
To drop a CHECK constraint, use the following SQL:
ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;
MySQL:
ALTER TABLE Persons
DROP CHECK CHK_PersonAge;
SQL DEFAULT Constraint
SQL DEFAULT Constraint
The DEFAULT constraint is used to set a default value for a column.
The default value will be added to all new records, if no other value is specified.
SQL DEFAULT on CREATE TABLE

The following SQL sets a DEFAULT value for the "City" column when the "Persons"
table is created:
My SQL / SQL Server / Oracle / MS Access:
ID int NOT NULL,
Age int,
City varchar(255) DEFAULT 'Sandnes'
);
The DEFAULT constraint can also be used to insert system values, by using

functions like GETDATE():
ID int NOT NULL,
OrderDate date DEFAULT GETDATE()
);
SQL DEFAULT on ALTER TABLE

To create a DEFAULT constraint on the "City" column when the table is already
MySQL:
ALTER TABLE Persons
ALTER City SET DEFAULT 'Sandnes';
SQL Server:
ALTER TABLE Persons
ADD CONSTRAINT df_City
DEFAULT 'Sandnes' FOR City;
MS Access:
ALTER TABLE Persons
ALTER COLUMN City SET DEFAULT 'Sandnes';
Oracle:
ALTER TABLE Persons
MODIFY City DEFAULT 'Sandnes';
DROP a DEFAULT Constraint
To drop a DEFAULT constraint, use the following SQL:
MySQL:
ALTER TABLE Persons
ALTER City DROP DEFAULT;
ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT;
SQL CREATE INDEX Statement
SQL CREATE INDEX Statement
The CREATE INDEX statement is used to create indexes in tables.
Indexes are used to retrieve data from the database more quickly than
otherwise. The users cannot see the indexes, they are just used to speed up
searches/queries.
Note: Updating a table with indexes takes more time than updating a table
without (because the indexes also need an update). So, only create indexes on
columns that will be frequently searched against.
CREATE INDEX Syntax

Creates an index on a table. Duplicate values are allowed:
CREATE INDEX index_name
ON table_name (column1, column2, ...);
CREATE UNIQUE INDEX Syntax

Creates a unique index on a table. Duplicate values are not allowed:
CREATE UNIQUE INDEX index_name
ON table_name (column1, column2, ...);
Note: The syntax for creating indexes varies among different databases.

Therefore: Check the syntax for creating indexes in your database.
CREATE INDEX Example

The SQL statement below creates an index named "idx_lastname" on the
"LastName" column in the "Persons" table:
CREATE INDEX idx_lastname
ON Persons (LastName);
If you want to create an index on a combination of columns, you can list the
column names within the parentheses, separated by commas:
CREATE INDEX idx_pname
ON Persons (LastName, FirstName);
DROP INDEX Statement

The DROP INDEX statement is used to delete an index in a table.
MS Access:
DROP INDEX index_name ON table_name;
SQL Server:
DROP INDEX table_name.index_name;
DB2/Oracle:
DROP INDEX index_name;
MySQL:
DROP INDEX index_name;
SQL AUTO INCREMENT Field
AUTO INCREMENT Field
Auto-increment allows a unique number to be generated automatically when a
new record is inserted into a table.
Often this is the primary key field that we would like to be created automatically
every time a new record is inserted.
Syntax for MySQL

The following SQL statement defines the "Personid" column to be an auto-
increment primary key field in the "Persons" table:
Personid int NOT NULL AUTO_INCREMENT,
Age int,
PRIMARY KEY (Personid)
);
MySQL uses the AUTO_INCREMENT keyword to perform an auto-increment feature.
By default, the starting value for AUTO_INCREMENT is 1, and it will increment by 1

for each new record.
To let the AUTO_INCREMENT sequence start with another value, use the following

SQL statement:
ALTER TABLE Persons AUTO_INCREMENT=100;
To insert a new record into the "Persons" table, we will NOT have to specify a
value for the "Personid" column (a unique value will be added automatically):
INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');
The SQL statement above would insert a new record into the "Persons" table.
The "Personid" column would be assigned a unique value. The "FirstName"
column would be set to "Lars" and the "LastName" column would be set to
"Monsen".
Syntax for SQL Server

Personid int IDENTITY(1,1) PRIMARY KEY,
Age int
);
The MS SQL Server uses the IDENTITY keyword to perform an auto-increment

feature.
In the example above, the starting value for IDENTITY is 1, and it will increment
by 1 for each new record.
Tip: To specify that the "Personid" column should start at value 10 and
increment by 5, change it to IDENTITY(10,5).
"Monsen".
Syntax for Access
Personid AUTOINCREMENT PRIMARY KEY,
Age int
);
The MS Access uses the AUTOINCREMENT keyword to perform an auto-increment

feature.
By default, the starting value for AUTOINCREMENT is 1, and it will increment by 1 for

each new record.
Tip: To specify that the "Personid" column should start at value 10 and
increment by 5, change the autoincrement to AUTOINCREMENT(10,5).
"Monsen".
Syntax for Oracle

In Oracle the code is a little bit more tricky.
You will have to create an auto-increment field with the sequence object (this
object generates a number sequence).
Use the following CREATE SEQUENCE syntax:
CREATE SEQUENCE seq_person
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10;
The code above creates a sequence object called seq_person, that starts with 1
and will increment by 1. It will also cache up to 10 values for performance. The
cache option specifies how many sequence values will be stored in memory for
faster access.
To insert a new record into the "Persons" table, we will have to use the nextval
function (this function retrieves the next value from seq_person sequence):
INSERT INTO Persons (Personid,FirstName,LastName)
VALUES (seq_person.nextval,'Lars','Monsen');
The "Personid" column would be assigned the next number from the seq_person
sequence. The "FirstName" column would be set to "Lars" and the "LastName"
column would be set to "Monsen".
SQL Working With Dates

SQL Dates
The most difficult part when working with dates is to be sure that the format of
the date you are trying to insert, matches the format of the date column in the
database.
As long as your data contains only the date portion, your queries will work as
expected. However, if a time portion is involved, it gets more complicated.
SQL Date Data Types

MySQL comes with the following data types for storing a date or a date/time
value in the database:
 DATE - format YYYY-MM-DD

 DATETIME - format: YYYY-MM-DD HH:MI:SS
 TIMESTAMP - format: YYYY-MM-DD HH:MI:SS
 YEAR - format YYYY or YY
SQL Server comes with the following data types for storing a date or a
date/time value in the database:
 DATE - format YYYY-MM-DD

 DATETIME - format: YYYY-MM-DD HH:MI:SS
 SMALLDATETIME - format: YYYY-MM-DD HH:MI:SS
 TIMESTAMP - format: a unique number
Note: The date types are chosen for a column when you create a new table in
your database!
SQL Working with Dates

Look at the following table:
Orders Table
OrderId ProductName OrderDate
1 Geitost 2008-11-11
2 Camembert Pierrot 2008-11-09
3 Mozzarella di Giovanni 2008-11-11
4 Mascarpone Fabioli 2008-10-29

Now we want to select the records with an OrderDate of "2008-11-11" from the
table above.
We use the following SELECT statement:
SELECT * FROM Orders WHERE OrderDate='2008-11-11'
The result-set will look like this:
1 Geitost 2008-11-11
3 Mozzarella di Giovanni 2008-11-11
Note: Two dates can easily be compared if there is no time component

involved!
Now, assume that the "Orders" table looks like this (notice the added time-
component in the "OrderDate" column):
1 Geitost 2008-11-11 13:23:44
2 Camembert Pierrot 2008-11-09 15:45:21
3 Mozzarella di Giovanni 2008-11-11 11:12:01

4 Mascarpone Fabioli 2008-10-29 14:56:59
If we use the same SELECT statement as above:
SELECT * FROM Orders WHERE OrderDate='2008-11-11'
we will get no result! This is because the query is looking only for dates with no
time portion.
Tip: To keep your queries simple and easy to maintain, do not use time-
components in your dates, unless you have to!
SQL Views
SQL CREATE VIEW Statement
In SQL, a view is a virtual table based on the result-set of an SQL statement.
A view contains rows and columns, just like a real table. The fields in a view are
fields from one or more real tables in the database.
You can add SQL statements and functions to a view and present the data as if
the data were coming from one single table.
A view is created with the CREATE VIEW statement.
CREATE VIEW Syntax

CREATE VIEW view_name AS
FROM table_name
WHERE condition;
Note: A view always shows up-to-date data! The database engine recreates the
view, every time a user queries it.
SQL CREATE VIEW Examples
The following SQL creates a view that shows all customers from Brazil:
Example
CREATE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName
FROM Customers
WHERE Country = 'Brazil';
Try it Yourself »
We can query the view above as follows:
Example
SELECT * FROM [Brazil Customers];
Try it Yourself »
The following SQL creates a view that selects every product in the "Products"
table with a price higher than the average price:
Example
CREATE VIEW [Products Above Average Price] AS
SELECT ProductName, Price
FROM Products
WHERE Price > (SELECT AVG(Price) FROM Products);
Try it Yourself »
We can query the view above as follows:
Example
SELECT * FROM [Products Above Average Price];
Try it Yourself »
SQL Updating a View

A view can be updated with the CREATE OR REPLACE VIEW statement.
SQL CREATE OR REPLACE VIEW Syntax
CREATE OR REPLACE VIEW view_name AS
FROM table_name
WHERE condition;
The following SQL adds the "City" column to the "Brazil Customers" view:
Example
CREATE OR REPLACE VIEW [Brazil Customers] AS
SELECT CustomerName, ContactName, City
FROM Customers
WHERE Country = 'Brazil';
Try it Yourself »
SQL Dropping a View

A view is deleted with the DROP VIEW statement.
SQL DROP VIEW Syntax

DROP VIEW view_name;
The following SQL drops the "Brazil Customers" view:
Example
DROP VIEW [Brazil Customers];
Try it Yourself »
SQL Injection
SQL Injection
SQL injection is a code injection technique that might destroy your database.
SQL injection is one of the most common web hacking techniques.
SQL injection is the placement of malicious code in SQL statements, via web
page input.
SQL in Web Pages

SQL injection usually occurs when you ask a user for input, like their
username/userid, and instead of a name/id, the user gives you an SQL
statement that you will unknowingly run on your database.
Look at the following example which creates a SELECT statement by adding a

variable (txtUserId) to a select string. The variable is fetched from user input
(getRequestString):
Example
txtUserId = getRequestString("UserId");
txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;
The rest of this chapter describes the potential dangers of using user input in
SQL statements.
SQL Injection Based on 1=1 is Always

True
Look at the example above again. The original purpose of the code was to
create an SQL statement to select a user, with a given user id.
If there is nothing to prevent a user from entering "wrong" input, the user can
enter some "smart" input like this:
105 OR 1=1
UserId:
Then, the SQL statement will look like this:
SELECT * FROM Users WHERE UserId = 105 OR 1=1;
The SQL above is valid and will return ALL rows from the "Users" table,
since OR 1=1 is always TRUE.
Does the example above look dangerous? What if the "Users" table contains
names and passwords?
The SQL statement above is much the same as this:
SELECT UserId, Name, Password FROM Users WHERE UserId = 105 or 1=1;
A hacker might get access to all the user names and passwords in a database,
by simply inserting 105 OR 1=1 into the input field.
SQL Injection Based on ""="" is Always

True
Here is an example of a user login on a web site:
Username:
John Doe
Password:
myPass
Example
uName = getRequestString("username");
uPass = getRequestString("userpassword");
sql = 'SELECT * FROM Users WHERE Name ="' + uName + '" AND Pass ="' +
uPass + '"'
Result
SELECT * FROM Users WHERE Name ="John Doe" AND Pass ="myPass"
A hacker might get access to user names and passwords in a database by

simply inserting " OR ""=" into the user name or password text box:
User Name:
Password:
The code at the server will create a valid SQL statement like this:
Result
SELECT * FROM Users WHERE Name ="" or ""="" AND Pass ="" or ""=""
The SQL above is valid and will return all rows from the "Users" table, since OR
""="" is always TRUE.
SQL Injection Based on Batched SQL

Statements
Most databases support batched SQL statement.
A batch of SQL statements is a group of two or more SQL statements,

separated by semicolons.
The SQL statement below will return all rows from the "Users" table, then delete
the "Suppliers" table.
Example
SELECT * FROM Users; DROP TABLE Suppliers
Look at the following example:
Example
txtSQL = "SELECT * FROM Users WHERE UserId = " + txtUserId;
And the following input:
105; DROP
User id:
The valid SQL statement would look like this:
Result
SELECT * FROM Users WHERE UserId = 105; DROP TABLE Suppliers;
Use SQL Parameters for Protection

To protect a web site from SQL injection, you can use SQL parameters.
SQL parameters are values that are added to an SQL query at execution time,
in a controlled manner.
ASP.NET Razor Example

txtSQL = "SELECT * FROM Users WHERE UserId = @0";
db.Execute(txtSQL,txtUserId);
Note that parameters are represented in the SQL statement by a @ marker.

The SQL engine checks each parameter to ensure that it is correct for its
column and are treated literally, and not as part of the SQL to be executed.
Another Example
txtNam = getRequestString("CustomerName");
txtAdd = getRequestString("Address");
txtCit = getRequestString("City");
txtSQL = "INSERT INTO Customers (CustomerName,Address,City)
Values(@0,@1,@2)";
db.Execute(txtSQL,txtNam,txtAdd,txtCit);
Examples
The following examples shows how to build parameterized queries in some
common web languages.
SELECT STATEMENT IN ASP.NET:
sql = "SELECT * FROM Customers WHERE CustomerId = @0";
command = new SqlCommand(sql);
command.Parameters.AddWithValue("@0",txtUserId);
command.ExecuteReader();
INSERT INTO STATEMENT IN ASP.NET:
txtNam = getRequestString("CustomerName");
txtAdd = getRequestString("Address");
txtCit = getRequestString("City");
txtSQL = "INSERT INTO Customers (CustomerName,Address,City)
Values(@0,@1,@2)";
command = new SqlCommand(txtSQL);
command.Parameters.AddWithValue("@0",txtNam);
command.Parameters.AddWithValue("@1",txtAdd);
command.Parameters.AddWithValue("@2",txtCit);
command.ExecuteNonQuery();
INSERT INTO STATEMENT IN PHP:

$stmt = $dbh->prepare("INSERT INTO Customers (CustomerName,Address,City)
VALUES (:nam, :add, :cit)");
$stmt->bindParam(':nam', $txtNam);
$stmt->bindParam(':add', $txtAdd);
$stmt->bindParam(':cit', $txtCit);
$stmt->execute();
SQL Hosting
SQL Hosting
If you want your web site to be able to store and retrieve data from a database,
your web server should have access to a database-system that uses the SQL
language.
If your web server is hosted by an Internet Service Provider (ISP), you will have
to look for SQL hosting plans.
The most common SQL hosting databases are MS SQL Server, Oracle, MySQL,
and MS Access.
MS SQL Server
Microsoft's SQL Server is a popular database software for database-driven web
sites with high traffic.
SQL Server is a very powerful, robust and full featured SQL database system.
Oracle
Oracle is also a popular database software for database-driven web sites with
high traffic.
Oracle is a very powerful, robust and full featured SQL database system.
MySQL
MySQL is also a popular database software for web sites.
MySQL is a very powerful, robust and full featured SQL database system.
MySQL is an inexpensive alternative to the expensive Microsoft and Oracle

solutions.
MS Access
When a web site requires only a simple database, Microsoft Access can be a
solution.
MS Access is not well suited for very high-traffic, and not as powerful as MySQL,
SQL Server, or Oracle.
SQL Data Types for MySQL, SQL

Server, and MS Access
The data type of a column defines what value the column can hold: integer,
character, money, date and time, binary, and so on.
SQL Data Types

Each column in a database table is required to have a name and a data type.
An SQL developer must decide what type of data that will be stored inside each
column when creating a table. The data type is a guideline for SQL to
understand what type of data is expected inside of each column, and it also
identifies how SQL will interact with the stored data.
Note: Data types might have different names in different database. And even if
the name is the same, the size and other details may be different! Always
check the documentation!
MySQL Data Types (Version 8.0)

In MySQL there are three main data types: string, numeric, and date and time.
String Data Types
Data type Description
CHAR(size) A FIXED length string (can contain letters, numbers, and special characters).
The size parameter specifies the column length in characters - can be from 0 to
255. Default is 1
VARCHAR(size) A VARIABLE length string (can contain letters, numbers, and special characters).
The size parameter specifies the maximum column length in characters - can be
from 0 to 65535
BINARY(size) Equal to CHAR(), but stores binary byte strings. The size parameter specifies the
column length in bytes. Default is 1
VARBINARY(size) Equal to VARCHAR(), but stores binary byte strings. The size parameter specifies
the maximum column length in bytes.
TINYBLOB For BLOBs (Binary Large Objects). Max length: 255 bytes
TINYTEXT Holds a string with a maximum length of 255 characters
TEXT(size) Holds a string with a maximum length of 65,535 bytes
BLOB(size) For BLOBs (Binary Large Objects). Holds up to 65,535 bytes of data
MEDIUMTEXT Holds a string with a maximum length of 16,777,215 characters
MEDIUMBLOB For BLOBs (Binary Large Objects). Holds up to 16,777,215 bytes of data
LONGTEXT Holds a string with a maximum length of 4,294,967,295 characters
LONGBLOB For BLOBs (Binary Large Objects). Holds up to 4,294,967,295 bytes of data
ENUM(val1, val2, val3, ...) A string object that can have only one value, chosen from a list of possible
values. You can list up to 65535 values in an ENUM list. If a value is inserted
that is not in the list, a blank value will be inserted. The values are sorted in the
order you enter them
SET(val1, val2, val3, ...) A string object that can have 0 or more values, chosen from a list of possible
values. You can list up to 64 values in a SET list
Numeric Data Types
BIT(size) A bit-value type. The number of bits per value is specified in size.
The size parameter can hold a value from 1 to 64. The default value for size is
1.
TINYINT(size) A very small integer. Signed range is from -128 to 127. Unsigned range is from
0 to 255. The size parameter specifies the maximum display width (which is
255)
BOOL Zero is considered as false, nonzero values are considered as true.
BOOLEAN Equal to BOOL
SMALLINT(size) A small integer. Signed range is from -32768 to 32767. Unsigned range is from
0 to 65535. The size parameter specifies the maximum display width (which is
255)
MEDIUMINT(size) A medium integer. Signed range is from -8388608 to 8388607. Unsigned

range is from 0 to 16777215. The size parameter specifies the maximum
display width (which is 255)
INT(size) A medium integer. Signed range is from -2147483648 to 2147483647.

Unsigned range is from 0 to 4294967295. The size parameter specifies the
maximum display width (which is 255)
INTEGER(size) Equal to INT(size)
BIGINT(size) A large integer. Signed range is from -9223372036854775808 to

9223372036854775807. Unsigned range is from 0 to
18446744073709551615. The size parameter specifies the maximum display
width (which is 255)
FLOAT(size, d) A floating point number. The total number of digits is specified in size. The
number of digits after the decimal point is specified in the d parameter. This
syntax is deprecated in MySQL 8.0.17, and it will be removed in future MySQL
versions
FLOAT(p) A floating point number. MySQL uses the p value to determine whether to use
FLOAT or DOUBLE for the resulting data type. If p is from 0 to 24, the data
type becomes FLOAT(). If p is from 25 to 53, the data type becomes DOUBLE()
DOUBLE(size, d) A normal-size floating point number. The total number of digits is specified
in size. The number of digits after the decimal point is specified in
the d parameter
DOUBLE PRECISION(size, d)
DECIMAL(size, d) An exact fixed-point number. The total number of digits is specified in size.
The number of digits after the decimal point is specified in the d parameter.
The maximum number for size is 65. The maximum number for d is 30. The
default value for size is 10. The default value for d is 0.
DEC(size, d) Equal to DECIMAL(size,d)

Note: All the numeric data types may have an extra option: UNSIGNED or
ZEROFILL. If you add the UNSIGNED option, MySQL disallows negative values
for the column. If you add the ZEROFILL option, MySQL automatically also adds
the UNSIGNED attribute to the column.
Date and Time Data Types
DATE A date. Format: YYYY-MM-DD. The supported range is from

'1000-01-01' to '9999-12-31'
DATETIME(fsp) A date and time combination. Format: YYYY-MM-DD

hh:mm:ss. The supported range is from '1000-01-01
00:00:00' to '9999-12-31 23:59:59'. Adding DEFAULT and
ON UPDATE in the column definition to get automatic
initialization and updating to the current date and time
TIMESTAMP(fsp) A timestamp. TIMESTAMP values are stored as the number

of seconds since the Unix epoch ('1970-01-01 00:00:00'
UTC). Format: YYYY-MM-DD hh:mm:ss. The supported
range is from '1970-01-01 00:00:01' UTC to '2038-01-09
03:14:07' UTC. Automatic initialization and updating to the
current date and time can be specified using DEFAULT
CURRENT_TIMESTAMP and ON UPDATE
CURRENT_TIMESTAMP in the column definition
TIME(fsp) A time. Format: hh:mm:ss. The supported range is from '-

838:59:59' to '838:59:59'
YEAR A year in four-digit format. Values allowed in four-digit

format: 1901 to 2155, and 0000.
MySQL 8.0 does not support year in two-digit format.
SQL Server Data Types

String Data Types
Data type Description Max size Storage
char(n) Fixed width character 8,000 characters Defined width

string
varchar(n) Variable width character 8,000 characters 2 bytes + number of

string chars
varchar(max) Variable width character 1,073,741,824 2 bytes + number of

string characters chars
text Variable width character 2GB of text data 4 bytes + number of

string chars
nchar Fixed width Unicode string 4,000 characters Defined width x 2

nvarchar Variable width Unicode 4,000 characters
string
nvarchar(max) Variable width Unicode 536,870,912 characters

string
ntext Variable width Unicode 2GB of text data

string
binary(n) Fixed width binary string 8,000 bytes
varbinary Variable width binary 8,000 bytes

string
varbinary(max) Variable width binary 2GB

string
image Variable width binary 2GB

string
Numeric Data Types
Data type Description Storage
bit Integer that can be 0, 1, or NULL

tinyint Allows whole numbers from 0 to 255 1 byte
smallint Allows whole numbers between -32,768 and 32,767 2 bytes
int Allows whole numbers between -2,147,483,648 and 2,147,483,647 4 bytes
bigint Allows whole numbers between -9,223,372,036,854,775,808 and 8 bytes

9,223,372,036,854,775,807
5-17 bytes
decimal(p,s) Fixed precision and scale numbers.
Allows numbers from -10^38 +1 to 10^38 –1.
The p parameter indicates the maximum total number of digits that can be
stored (both to the left and to the right of the decimal point). p must be a
value from 1 to 38. Default is 18.
The s parameter indicates the maximum number of digits stored to the

right of the decimal point. s must be a value from 0 to p. Default value is 0
numeric(p,s) Fixed precision and scale numbers. 5-17 bytes
Allows numbers from -10^38 +1 to 10^38 –1.
The p parameter indicates the maximum total number of digits that can be
stored (both to the left and to the right of the decimal point). p must be a
value from 1 to 38. Default is 18.
The s parameter indicates the maximum number of digits stored to the

right of the decimal point. s must be a value from 0 to p. Default value is 0
smallmoney Monetary data from -214,748.3648 to 214,748.3647 4 bytes
money Monetary data from -922,337,203,685,477.5808 to 8 bytes

922,337,203,685,477.5807
float(n) Floating precision number data from -1.79E + 308 to 1.79E + 308. 4 or 8 bytes
The n parameter indicates whether the field should hold 4 or 8 bytes.

float(24) holds a 4-byte field and float(53) holds an 8-byte field. Default
value of n is 53.
real Floating precision number data from -3.40E + 38 to 3.40E + 38 4 bytes
Date and Time Data Types
datetime From January 1, 1753 to December 31, 9999 with an accuracy of 3.33 8 bytes
milliseconds
datetime2 From January 1, 0001 to December 31, 9999 with an accuracy of 100 6-8 bytes
nanoseconds
smalldatetime From January 1, 1900 to June 6, 2079 with an accuracy of 1 minute 4 bytes
date Store a date only. From January 1, 0001 to December 31, 9999 3 bytes
time Store a time only to an accuracy of 100 nanoseconds 3-5 bytes
datetimeoffset The same as datetime2 with the addition of a time zone offset 8-10 bytes
timestamp Stores a unique number that gets updated every time a row gets created or
modified. The timestamp value is based upon an internal clock and does not
correspond to real time. Each table may have only one timestamp variable
Other Data Types
sql_variant Stores up to 8,000 bytes of data of various data types, except text,
ntext, and timestamp
uniqueidentifie Stores a globally unique identifier (GUID)

r
xml Stores XML formatted data. Maximum 2GB
cursor Stores a reference to a cursor used for database operations
table Stores a result-set for later processing
MS Access Data Types

Text Use for text or combinations of text and numbers. 255 characters maximum
Memo Memo is used for larger amounts of text. Stores up to 65,536

characters. Note: You cannot sort a memo field. However, they are searchable
Byte Allows whole numbers from 0 to 255 1 byte
Integer Allows whole numbers between -32,768 and 32,767 2 bytes
Long Allows whole numbers between -2,147,483,648 and 2,147,483,647 4 bytes
Single Single precision floating-point. Will handle most decimals 4 bytes
Double Double precision floating-point. Will handle most decimals 8 bytes
Currency Use for currency. Holds up to 15 digits of whole dollars, plus 4 decimal 8 bytes
places. Tip: You can choose which country's currency to use
AutoNumber AutoNumber fields automatically give each record its own number, usually 4 bytes
starting at 1
Date/Time Use for dates and times 8 bytes

Yes/No A logical field can be displayed as Yes/No, True/False, or On/Off. In code, use 1 bit
the constants True and False (equivalent to -1 and 0). Note: Null values are not
allowed in Yes/No fields
Ole Object Can store pictures, audio, video, or other BLOBs (Binary Large Objects) up to 1GB
Hyperlink Contain links to other files, including web pages
Lookup Wizard Let you type a list of options, which can then be chosen from a drop-down list 4 bytes
SQL Keywords Reference

This SQL keywords reference contains the reserved words in SQL.
SQL Keywords
Keyword Description
ADD Adds a column in an existing table
ADD CONSTRAINT Adds a constraint after a table is already created
ALTER Adds, deletes, or modifies columns in a table, or

changes the data type of a column in a table
ALTER COLUMN Changes the data type of a column in a table
ALTER TABLE Adds, deletes, or modifies columns in a table
ALL Returns true if all of the subquery values meet the

condition
AND Only includes rows where both conditions is true
ANY Returns true if any of the subquery values meet the

condition
AS Renames a column or table with an alias
ASC Sorts the result set in ascending order
BACKUP DATABASE Creates a back up of an existing database
BETWEEN Selects values within a given range
CASE Creates different outputs based on conditions

CHECK A constraint that limits the value that can be placed in
a column
COLUMN Changes the data type of a column or deletes a

column in a table
CONSTRAINT Adds or deletes a constraint
CREATE Creates a database, index, view, table, or procedure
CREATE DATABASE Creates a new SQL database
CREATE INDEX Creates an index on a table (allows duplicate values)
CREATE OR REPLACE VIEW Updates a view
CREATE TABLE Creates a new table in the database
CREATE PROCEDURE Creates a stored procedure
CREATE UNIQUE INDEX Creates a unique index on a table (no duplicate

values)
CREATE VIEW Creates a view based on the result set of a SELECT
statement
DATABASE Creates or deletes an SQL database
DEFAULT A constraint that provides a default value for a column
DELETE Deletes rows from a table
DESC Sorts the result set in descending order
DISTINCT Selects only distinct (different) values
DROP Deletes a column, constraint, database, index, table,

or view
DROP COLUMN Deletes a column in a table
DROP CONSTRAINT Deletes a UNIQUE, PRIMARY KEY, FOREIGN KEY, or

CHECK constraint
DROP DATABASE Deletes an existing SQL database

DROP DEFAULT Deletes a DEFAULT constraint
DROP INDEX Deletes an index in a table
DROP TABLE Deletes an existing table in the database
DROP VIEW Deletes a view
EXEC Executes a stored procedure
EXISTS Tests for the existence of any record in a subquery
FOREIGN KEY A constraint that is a key used to link two tables

together
FROM Specifies which table to select or delete data from
FULL OUTER JOIN Returns all rows when there is a match in either left
table or right table
GROUP BY Groups the result set (used with aggregate functions:

COUNT, MAX, MIN, SUM, AVG)
HAVING Used instead of WHERE with aggregate functions
IN Allows you to specify multiple values in a WHERE

clause
INDEX Creates or deletes an index in a table
INNER JOIN Returns rows that have matching values in both tables
INSERT INTO Inserts new rows in a table
INSERT INTO SELECT Copies data from one table into another table
IS NULL Tests for empty values
IS NOT NULL Tests for non-empty values
JOIN Joins tables
LEFT JOIN Returns all rows from the left table, and the matching
rows from the right table
LIKE Searches for a specified pattern in a column

LIMIT Specifies the number of records to return in the result
set
NOT Only includes rows where a condition is not true
NOT NULL A constraint that enforces a column to not accept

NULL values
OR Includes rows where either condition is true
ORDER BY Sorts the result set in ascending or descending order
OUTER JOIN Returns all rows when there is a match in either left
table or right table
PRIMARY KEY A constraint that uniquely identifies each record in a

database table
PROCEDURE A stored procedure
RIGHT JOIN Returns all rows from the right table, and the
matching rows from the left table
ROWNUM Specifies the number of records to return in the result

set
SELECT Selects data from a database
SELECT DISTINCT Selects only distinct (different) values
SELECT INTO Copies data from one table into a new table
SELECT TOP Specifies the number of records to return in the result

set
SET Specifies which columns and values that should be

updated in a table
TABLE Creates a table, or adds, deletes, or modifies columns

in a table, or deletes a table or data inside a table
TOP Specifies the number of records to return in the result

set
TRUNCATE TABLE Deletes the data inside a table, but not the table itself
UNION Combines the result set of two or more SELECT

statements (only distinct values)
UNION ALL Combines the result set of two or more SELECT
statements (allows duplicate values)
UNIQUE A constraint that ensures that all values in a column

are unique
UPDATE Updates existing rows in a table
VALUES Specifies the values of an INSERT INTO statement
VIEW Creates, updates, or deletes a view
WHERE Filters a result set to include only records that fulfill a

specified condition
MySQL Functions
MySQL has many built-in functions.
This reference contains string, numeric, date, and some advanced functions
in MySQL.
MySQL String Functions
Function Description
ASCII Returns the ASCII value for the specific character
CHAR_LENGTH Returns the length of a string (in characters)
CHARACTER_LENGTH Returns the length of a string (in characters)
CONCAT Adds two or more expressions together
CONCAT_WS Adds two or more expressions together with a separator
FIELD Returns the index position of a value in a list of values
FIND_IN_SET Returns the position of a string within a list of strings
FORMAT Formats a number to a format like "#,###,###.##",

rounded to a specified number of decimal places
INSERT Inserts a string within a string at the specified position and

for a certain number of characters
INSTR Returns the position of the first occurrence of a string in
another string
LCASE Converts a string to lower-case
LEFT Extracts a number of characters from a string (starting from

left)
LENGTH Returns the length of a string (in bytes)
LOCATE Returns the position of the first occurrence of a substring in

a string
LOWER Converts a string to lower-case
LPAD Left-pads a string with another string, to a certain length
LTRIM Removes leading spaces from a string
MID Extracts a substring from a string (starting at any position)
POSITION Returns the position of the first occurrence of a substring in

a string
REPEAT Repeats a string as many times as specified
REPLACE Replaces all occurrences of a substring within a string, with

a new substring
REVERSE Reverses a string and returns the result
RIGHT Extracts a number of characters from a string (starting from

right)
RPAD Right-pads a string with another string, to a certain length
RTRIM Removes trailing spaces from a string
SPACE Returns a string of the specified number of space characters
STRCMP Compares two strings
SUBSTR Extracts a substring from a string (starting at any position)
SUBSTRING Extracts a substring from a string (starting at any position)

SUBSTRING_INDEX Returns a substring of a string before a specified number of
delimiter occurs
TRIM Removes leading and trailing spaces from a string
UCASE Converts a string to upper-case
UPPER Converts a string to upper-case
MySQL Numeric Functions
ABS Returns the absolute value of a number
ACOS Returns the arc cosine of a number
ASIN Returns the arc sine of a number
ATAN Returns the arc tangent of one or two numbers

ATAN2 Returns the arc tangent of two numbers
AVG Returns the average value of an expression
CEIL Returns the smallest integer value that is >= to a number
CEILING Returns the smallest integer value that is >= to a number
COS Returns the cosine of a number
COT Returns the cotangent of a number
COUNT Returns the number of records returned by a select query
DEGREES Converts a value in radians to degrees
DIV Used for integer division
EXP Returns e raised to the power of a specified number
FLOOR Returns the largest integer value that is <= to a number

GREATEST Returns the greatest value of the list of arguments
LEAST Returns the smallest value of the list of arguments
LN Returns the natural logarithm of a number
LOG Returns the natural logarithm of a number, or the logarithm of

a number to a specified base
LOG10 Returns the natural logarithm of a number to base 10
MAX Returns the maximum value in a set of values
MIN Returns the minimum value in a set of values
MOD Returns the remainder of a number divided by another number
PI Returns the value of PI
POW Returns the value of a number raised to the power of another

number
POWER Returns the value of a number raised to the power of another

number
RADIANS Converts a degree value into radians
RAND Returns a random number
ROUND Rounds a number to a specified number of decimal places
SIGN Returns the sign of a number
SIN Returns the sine of a number
SQRT Returns the square root of a number
SUM Calculates the sum of a set of values
TAN Returns the tangent of a number
TRUNCATE Truncates a number to the specified number of decimal places

MySQL Date Functions
ADDDATE Adds a time/date interval to a date and then returns the

date
ADDTIME Adds a time interval to a time/datetime and then returns

the time/datetime
CURDATE Returns the current date
CURRENT_DATE Returns the current date
CURRENT_TIME Returns the current time
CURRENT_TIMESTAM Returns the current date and time

P
CURTIME Returns the current time
DATE Extracts the date part from a datetime expression

DATEDIFF Returns the number of days between two date values
DATE_ADD Adds a time/date interval to a date and then returns the

date
DATE_FORMAT Formats a date
DATE_SUB Subtracts a time/date interval from a date and then returns

the date
DAY Returns the day of the month for a given date
DAYNAME Returns the weekday name for a given date
DAYOFMONTH Returns the day of the month for a given date
DAYOFWEEK Returns the weekday index for a given date
DAYOFYEAR Returns the day of the year for a given date
EXTRACT Extracts a part from a given date

FROM_DAYS Returns a date from a numeric datevalue
HOUR Returns the hour part for a given date
LAST_DAY Extracts the last day of the month for a given date
LOCALTIME Returns the current date and time
LOCALTIMESTAMP Returns the current date and time
MAKEDATE Creates and returns a date based on a year and a number

of days value
MAKETIME Creates and returns a time based on an hour, minute, and

second value
MICROSECOND Returns the microsecond part of a time/datetime
MINUTE Returns the minute part of a time/datetime
MONTH Returns the month part for a given date

MONTHNAME Returns the name of the month for a given date
NOW Returns the current date and time
PERIOD_ADD Adds a specified number of months to a period
PERIOD_DIFF Returns the difference between two periods
QUARTER Returns the quarter of the year for a given date value
SECOND Returns the seconds part of a time/datetime
SEC_TO_TIME Returns a time value based on the specified seconds
STR_TO_DATE Returns a date based on a string and a format
SUBDATE Subtracts a time/date interval from a date and then returns

the date
SUBTIME Subtracts a time interval from a datetime and then returns

the time/datetime
SYSDATE Returns the current date and time
TIME Extracts the time part from a given time/datetime
TIME_FORMAT Formats a time by a specified format
TIME_TO_SEC Converts a time value into seconds
TIMEDIFF Returns the difference between two time/datetime

expressions
TIMESTAMP Returns a datetime value based on a date or datetime value
TO_DAYS Returns the number of days between a date and date

"0000-00-00"
WEEK Returns the week number for a given date
WEEKDAY Returns the weekday number for a given date
WEEKOFYEAR Returns the week number for a given date
YEAR Returns the year part for a given date

YEARWEEK Returns the year and week number for a given date
MySQL Advanced Functions
BIN Returns a binary representation of a number
BINARY Converts a value to a binary string
CASE Goes through conditions and return a value when the first
condition is met
CAST Converts a value (of any type) into a specified datatype
COALESCE Returns the first non-null value in a list
CONNECTION_ID Returns the unique connection ID for the current connection
CONV Converts a number from one numeric base system to another

CONVERT Converts a value into the specified datatype or character set
CURRENT_USER Returns the user name and host name for the MySQL account
that the server used to authenticate the current client
DATABASE Returns the name of the current database
IF Returns a value if a condition is TRUE, or another value if a

condition is FALSE
IFNULL Return a specified value if the expression is NULL, otherwise

return the expression
ISNULL Returns 1 or 0 depending on whether an expression is NULL
LAST_INSERT_ID Returns the AUTO_INCREMENT id of the last row that has been
inserted or updated in a table
NULLIF Compares two expressions and returns NULL if they are equal.
Otherwise, the first expression is returned
SESSION_USER Returns the current MySQL user name and host name
SYSTEM_USER Returns the current MySQL user name and host name
USER Returns the current MySQL user name and host name
VERSION Returns the current version of the MySQL database
SQL Server Functions
SQL Server has many built-in functions.
This reference contains string, numeric, date, conversion, and some

advanced functions in SQL Server.
SQL Server String Functions
ASCII Returns the ASCII value for the specific character
CHAR Returns the character based on the ASCII code
CHARINDEX Returns the position of a substring in a string
CONCAT Adds two or more strings together
Concat with + Adds two or more strings together

CONCAT_WS Adds two or more strings together with a separator
DATALENGTH Returns the number of bytes used to represent an expression
DIFFERENCE Compares two SOUNDEX values, and returns an integer value
FORMAT Formats a value with the specified format
LEFT Extracts a number of characters from a string (starting from

left)
LEN Returns the length of a string
LOWER Converts a string to lower-case
LTRIM Removes leading spaces from a string
NCHAR Returns the Unicode character based on the number code
PATINDEX Returns the position of a pattern in a string
QUOTENAME Returns a Unicode string with delimiters added to make the

string a valid SQL Server delimited identifier
REPLACE Replaces all occurrences of a substring within a string, with a
new substring
REPLICATE Repeats a string a specified number of times
REVERSE Reverses a string and returns the result
RIGHT Extracts a number of characters from a string (starting from

right)
RTRIM Removes trailing spaces from a string
SOUNDEX Returns a four-character code to evaluate the similarity of two

strings
SPACE Returns a string of the specified number of space characters
STR Returns a number as string
STUFF Deletes a part of a string and then inserts another part into the
string, starting at a specified position
SUBSTRING Extracts some characters from a string

TRANSLATE Returns the string from the first argument after the characters
specified in the second argument are translated into the
characters specified in the third argument.
TRIM Removes leading and trailing spaces (or other specified

characters) from a string
UNICODE Returns the Unicode value for the first character of the input
expression
UPPER Converts a string to upper-case
SQL Server Math/Numeric Functions
ABS Returns the absolute value of a number
ACOS Returns the arc cosine of a number
ASIN Returns the arc sine of a number

ATAN Returns the arc tangent of a number
ATN2 Returns the arc tangent of two numbers
AVG Returns the average value of an expression
CEILING Returns the smallest integer value that is >= a number
COUNT Returns the number of records returned by a select query
COS Returns the cosine of a number
COT Returns the cotangent of a number
DEGREES Converts a value in radians to degrees
EXP Returns e raised to the power of a specified number
FLOOR Returns the largest integer value that is <= to a number
LOG Returns the natural logarithm of a number, or the logarithm of

a number to a specified base
MAX Returns the maximum value in a set of values
MIN Returns the minimum value in a set of values
PI Returns the value of PI
POWER Returns the value of a number raised to the power of another

number
RADIANS Converts a degree value into radians
RAND Returns a random number
ROUND Rounds a number to a specified number of decimal places
SIGN Returns the sign of a number
SIN Returns the sine of a number
SQRT Returns the square root of a number

SQUARE Returns the square of a number
SUM Calculates the sum of a set of values
TAN Returns the tangent of a number
SQL Server Date Functions
CURRENT_TIMESTAMP Returns the current date and time
DATEADD Adds a time/date interval to a date and then returns the date
DATEDIFF Returns the difference between two dates
DATEFROMPARTS Returns a date from the specified parts (year, month, and
day values)
DATENAME Returns a specified part of a date (as string)

DATEPART Returns a specified part of a date (as integer)
DAY Returns the day of the month for a specified date
GETDATE Returns the current database system date and time
GETUTCDATE Returns the current database system UTC date and time
ISDATE Checks an expression and returns 1 if it is a valid date,

otherwise 0
MONTH Returns the month part for a specified date (a number from
1 to 12)
SYSDATETIME Returns the date and time of the SQL Server
YEAR Returns the year part for a specified date
SQL Server Advanced Functions
CAST Converts a value (of any type) into a specified datatype
COALESCE Returns the first non-null value in a list
CONVERT Converts a value (of any type) into a specified datatype
CURRENT_USER Returns the name of the current user in the SQL Server
database
IIF Returns a value if a condition is TRUE, or another value if a

condition is FALSE
ISNULL Return a specified value if the expression is NULL, otherwise

return the expression
ISNUMERIC Tests whether an expression is numeric
NULLIF Returns NULL if two expressions are equal
SESSION_USER Returns the name of the current user in the SQL Server
database
SESSIONPROPERT Returns the session settings for a specified option

Y
SYSTEM_USER Returns the login name for the current user
USER_NAME Returns the database user name based on the specified id
MS Access Functions
MS Access has many built-in functions.
This reference contains the string, numeric, and date functions in MS Access.
MS Access String Functions
Asc Returns the ASCII value for the specific character
Chr Returns the character for the specified ASCII number code
Concat with & Adds two or more strings together
CurDir Returns the full path for a specified drive

Format Formats a value with the specified format
InStr Gets the position of the first occurrence of a string in another
InstrRev Gets the position of the first occurrence of a string in another,

from the end of string
LCase Converts a string to lower-case
Left Extracts a number of characters from a string (starting from left)
Len Returns the length of a string
LTrim Removes leading spaces from a string
Mid Extracts some characters from a string (starting at any position)
Replace Replaces a substring within a string, with another substring, a

specified number of times
Right Extracts a number of characters from a string (starting from

right)
RTrim Removes trailing spaces from a string
Space Returns a string of the specified number of space characters
Split Splits a string into an array of substrings
Str Returns a number as string
StrComp Compares two strings
StrConv Returns a converted string
StrReverse Reverses a string and returns the result
Trim Removes both leading and trailing spaces from a string
UCase Converts a string to upper-case

MS Access Numeric Functions
Abs Returns the absolute value of a number
Atn Returns the arc tangent of a number
Avg Returns the average value of an expression
Cos Returns the cosine of an angle
Count Returns the number of records returned by a select query
Exp Returns e raised to the power of a specified number
Fix Returns the integer part of a number
Format Formats a numeric value with the specified format
Int Returns the integer part of a number

Max Returns the maximum value in a set of values
Min Returns the minimum value in a set of values
Randomize Initializes the random number generator (used by Rnd()) with a

seed
Rnd Returns a random number
Round Rounds a number to a specified number of decimal places
Sgn Returns the sign of a number
Sqr Returns the square root of a number
Sum Calculates the sum of a set of values
Val Reads a string and returns the numbers found in the string
MS Access Date Functions
Date Returns the current system date
DateAdd Adds a time/date interval to a date and then returns the date
DateDiff Returns the difference between two dates
DatePart Returns a specified part of a date (as an integer)
DateSerial Returns a date from the specified parts (year, month, and day
values)
DateValue Returns a date based on a string
Day Returns the day of the month for a given date
Format Formats a date value with the specified format
Hour Returns the hour part of a time/datetime

Minute Returns the minute part of a time/datetime
Month Returns the month part of a given date
MonthName Returns the name of the month based on a number
Now Returns the current date and time based on the computer's
system date and time
Second Returns the seconds part of a time/datetime
Time Returns the current system time
TimeSerial Returns a time from the specified parts (hour, minute, and
second value)
TimeValue Returns a time based on a string
Weekday Returns the weekday number for a given date
WeekdayName Returns the weekday name based on a number

Year Returns the year part of a given date
MS Access Some Other Functions
CurrentUser Returns the name of the current database user
Environ Returns a string that contains the value of an operating system

environment variable
IsDate Checks whether an expression can be converted to a date
IsNull Checks whether an expression contains Null (no data)
IsNumeric Checks whether an expression is a valid number
SQL Quick Reference from
W3Schools
SQL Statement Syntax
AND / OR SELECT column_name(s)

FROM table_name
WHERE condition
AND|OR condition
ALTER TABLE ALTER TABLE table_name

ADD column_name datatype
or

DROP COLUMN column_name
AS (alias) SELECT column_name AS column_alias

FROM table_name
or
SELECT column_name
FROM table_name AS table_alias
BETWEEN SELECT column_name(s)

FROM table_name
WHERE column_name
BETWEEN value1 AND value2
CREATE DATABASE CREATE DATABASE database_name
CREATE TABLE CREATE TABLE table_name

(
column_name1 data_type,
...
)
CREATE INDEX CREATE INDEX index_name
ON table_name (column_name)
or
CREATE UNIQUE INDEX index_name

ON table_name (column_name)
CREATE VIEW CREATE VIEW view_name AS

FROM table_name
WHERE condition
DELETE DELETE FROM table_name

WHERE some_column=some_value
or
DELETE FROM table_name

(Note: Deletes the entire table!!)
DELETE * FROM table_name

(Note: Deletes the entire table!!)
DROP DATABASE DROP DATABASE database_name
DROP INDEX DROP INDEX table_name.index_name (SQL Server)

DROP INDEX index_name ON table_name (MS Access)
DROP INDEX index_name (DB2/Oracle)
DROP INDEX index_name (MySQL)
DROP TABLE DROP TABLE table_name
EXISTS IF EXISTS (SELECT * FROM table_name WHERE id = ?)

BEGIN
--do what needs to be done if exists
END
ELSE
BEGIN
--do what needs to be done if not
END
GROUP BY SELECT column_name, aggregate_function(column_name)

FROM table_name
WHERE column_name operator value
GROUP BY column_name
HAVING SELECT column_name, aggregate_function(column_name)

FROM table_name
GROUP BY column_name
HAVING aggregate_function(column_name) operator value
IN SELECT column_name(s)
FROM table_name
WHERE column_name
IN (value1,value2,..)
INSERT INTO INSERT INTO table_name

VALUES (value1, value2, value3,....)
or
INSERT INTO table_name

(column1, column2, column3,...)
VALUES (value1, value2, value3,....)
INNER JOIN SELECT column_name(s)

FROM table_name1
INNER JOIN table_name2
ON table_name1.column_name=table_name2.column_name
LEFT JOIN SELECT column_name(s)

FROM table_name1
LEFT JOIN table_name2
RIGHT JOIN SELECT column_name(s)

FROM table_name1
RIGHT JOIN table_name2
FULL JOIN SELECT column_name(s)

FROM table_name1
FULL JOIN table_name2
LIKE SELECT column_name(s)
FROM table_name
WHERE column_name LIKE pattern
ORDER BY SELECT column_name(s)

FROM table_name
ORDER BY column_name [ASC|DESC]
SELECT SELECT column_name(s)

FROM table_name
SELECT * SELECT *
FROM table_name
SELECT DISTINCT SELECT DISTINCT column_name(s)

FROM table_name
SELECT INTO SELECT *

INTO new_table_name [IN externaldatabase]
FROM old_table_name
or
INTO new_table_name [IN externaldatabase]
FROM old_table_name
SELECT TOP SELECT TOP number|percent column_name(s)

FROM table_name
TRUNCATE TABLE TRUNCATE TABLE table_name
UNION SELECT column_name(s) FROM table_name1

UNION
SELECT column_name(s) FROM table_name2
UNION ALL SELECT column_name(s) FROM table_name1

UNION ALL
SELECT column_name(s) FROM table_name2
UPDATE UPDATE table_name

SET column1=value, column2=value,...
WHERE some_column=some_value
WHERE SELECT column_name(s)
FROM table_name

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Introduction to

What Can SQL do?

SQL is a Standard - BUT....

 An RDBMS database program (i.e. MS Access, SQL Server, MySQL)

The data in RDBMS is stored in database objects called tables. A table is a

Look at the "Customers" table:

A column is a vertical entity in a table that contains all information

Below is a selection from the "Customers" table:

CustomerI CustomerName ContactName Address City PostalCode Country

1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Ana Trujillo Avda. de la México 05021 Mexico

3 Antonio Moreno Antonio Mataderos 2312 México 05023 Mexico

Keep in Mind That...

In this tutorial we will write all SQL keywords in upper-case.

Semicolon after SQL Statements?

Semicolon is the standard way to separate each SQL statement in database

Some of The Most Important SQL

The data returned is stored in a result table, called the result-set.

CustomerI CustomerName ContactName Address City PostalCod Country

1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Ana Trujillo Avda. de la México 05021 Mexico

3 Antonio Moreno Antonio Mataderos 2312 México 05023 Mexico

5 Berglunds Christina Berguvsvägen 8 Luleå S-958 22 Sweden

SELECT DISTINCT Syntax

CustomerID CustomerName ContactName Address City PostalCode Country

1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Ana Trujillo Avda. de la México 05021 Mexico

3 Antonio Moreno Antonio Mataderos 2312 México 05023 Mexico

5 Berglunds Christina Berguvsvägen 8 Luleå S-958 22 Sweden

SELECT Example Without DISTINCT

Now, let us use the SELECT DISTINCT statement and see the result.

SELECT DISTINCT Examples

Note: The example above will not work in Firefox! Because

Here is the workaround for MS Access:

It is used to extract only those records that fulfill a specified condition.

Note: The WHERE clause is not only used in SELECT statements, it is also used

1 Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Ana Trujillo Avda. de la México 05021 Mexico

3 Antonio Moreno Antonio Mataderos 2312 México 05023 Mexico

5 Berglunds snabbköp Christina Berguvsvägen 8 Luleå S-958 22 Sweden

WHERE Clause Example

Text Fields vs. Numeric Fields

However, numeric fields should not be enclosed in quotes:

Operator Description Example

> Greater than Try it

< Less than Try it

>= Greater than or equal Try it

<= Less than or equal Try it

<> Not equal. Note: In some versions of SQL this operator Try it

BETWEEN Between a certain range Try it

LIKE Search for a pattern Try it

The AND and OR operators are used to filter records based on more than one

 The AND operator displays a record if all the conditions separated

The NOT operator displays a record if the condition(s) is NOT TRUE.

1 Alfreds Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Ana Trujillo Avda. de la México D.F. 05021 Mexico

3 Antonio Antonio Mataderos México D.F. 05023 Mexico

4 Around the Thomas Hardy 120 Hanover London WA1 1DP UK