Introduction To SQL

1.
Introduction to SQL
1.1. Overview of SQL
What is SQL?
 SQL stands for Structured Query Language

 SQL lets you access and manipulate databases
 SQL is an ANSI (American National Standards Institute) standard
 SQL is a standard language for accessing and manipulating databases.
 SQL is a nonprocedural language. We can use SQL to tell what data to retrieve or
modify without telling it how to do its job. SQL does not provide any flow of- control
programming constructs, function definitions, do-loops, or if-then-else statements.
 SQL is a widely used database language, providing means of data manipulation
(store, retrieve, update, delete) and database creation.
1.2. History of SQL

During the 1970s, a group at IBM San Jose Research Laboratory developed the System R
relational database management system, based on the model introduced by Edgar F.
Codd in his influential paper, A Relational Model of Data for Large Shared Data Banks.
The acronym SEQUEL was later changed to SQL because "SEQUEL" was a trademark of
the UK-based Hawker Siddeley aircraft company.
1.3. Function of SQL

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
Structured Query Language 1

 Although SQL is an ANSI (American National Standards Institute) standard, there
are many 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.
 provides a fixed set of data types in particular for strings of different length char(n),
varchar(n), longvarchar(n)
1.4. SQL Components
1. Data Manipulation Language (DML), which retrieves or modifies data

2. Data Definition Language (DDL), which defines the structure of the data
3. Data Control Language (DCL), which defines the privileges granted to
database users.
1.4.1. SQL DML
 The category of DML contains four basic statements. These statements are used
most often by application developers.
1. SELECT - extracts data from a database
- Which retrieves rows from a table.
- The SELECT statement specifies which columns to include in the result
set.
- The vast majority of the SQL commands used in applications are
SELECT statements.
2. UPDATE - updates data in a database
- Which modifies existing rows in a table.
- In other words it changes an existing value in a column of a table.
3. DELETE - deletes data from a database
- which removes a specified row or a set of rows from a table.
4. INSERT INTO/ insert - inserts new data into a database
-Which adds rows to a table.
-INSERT is used to populate a newly-created table or to add a new row
(or rows) to an already-existing table.

1.4.2. SQL DDL
 DDL and DCL statements are commonly used by a database designer and
database administrator for establishing the database structures used by an
application.
 The DDL part of SQL permits database tables to be created or deleted. It also
defines indexes (keys), specify links between tables, and impose constraints
between tables. The most important DDL statements in SQL are:
1. CREATE DATABASE - creates a new database

2. ALTER DATABASE - modifies a database
3. CREATE TABLE - creates a new table
- Creates a table with the column names the user provides. The user also
needs to specify the data type for each column. Unfortunately, data
types vary slightly from one RDBMS to another, so that user might
need metadata to establish the data types used for a particular
database.
- It is normally used less often than the data manipulation commands
because a table is created only once, whereas inserting and deleting
rows or changing individual values generally occurs more frequently.
4. ALTER TABLE - modifies a table
-Adds or removes a column from a table.
-This command is used in connection with ADD, MODIFY and
DROP.
5. DROP TABLE - deletes a table
-Deletes all rows and removes the table definition from the
database.
6. CREATE INDEX - creates an index (search key)

7. DROP INDEX - deletes an index
Changes to the structure of a database are handled by a different set of SQL

statements, called the SQL data Definition Languages, or DDL.

In short, using DDL statements, you can:
o Define and create a new table, using CREATE
o Remove a table that’s no longer needed, using DROP
o Changes the definition of an existing table, using ALTER
o Define a virtual table(or view) of a data
o Establish security controls for a database
o Build an index to make table access faster
o Control the physical storage of data by the DBMS
1.4.3. SQL DCL
• GRANT
• REVOKE
• DENAY

2. SQL Basic
2.1. Language elements
The SQL language is sub-divided into several language elements, including:
 Statements : which may have a persistent effect on schemas and data, or which may
control transactions, program flow, connections, sessions, or diagnostics.
 Queries: which retrieve data based on specific criteria.
 Expressions: which can produce either scalar values or tables consisting of columns
and rows of data.
 Predicates: specify conditions that can be evaluated to SQL three-valued logic
(3VL) Boolean truth values and which are used to limit the effects of statements and
queries, or to change program flow.
 Clauses: are optional, constituent components of statements and queries.
 Whitespace is generally ignored in SQL statements and queries, making it easier to
format SQL code for readability.
 SQL statements also include the semicolon (";") statement terminator. Though not
required on every platform, it is defined as a standard part of the SQL grammar.
2.2 Introduction to SQL Statement/ commands

The SQL languages consist of many statements, which are summarized below. Each
statement requests a specific action from the DBMS, such as creating a new table,
retrieving data, or inserting new data into the database.
Statement Descriptions
Data Manipulation
SELECT Retrieve data from the database
INSERT Adds new rows of the data to the database
DELETE Removes rows of the data from the database
UPDATE Modifies existing database data
Data Definition
CREATE TABLE Adds a new table to the database
DROP TABLE Removes a table from the database
ALTER TABLE Change the structure of an existing table
CREATE VIEW Adds a new view to the database
DROP VIEW Removes a view from the database

CREATE INDEX Builds an index for a column
DROP INDEX Remove an index for a column
CREATE SYNOMY Define an alias for a table name
DROP SYNOMY Remove an alias for a table name
COMMENT Defines a remarks for a table or column
LABEL Defines a little for a table or column
Access Control
GRANT Grant user access privileges
REVOKE Removes user access privileges

DENY
Table 2.1: Major SQL statement
All SQL statements have the same basic form. i.e all SQL statements has similar
structures
Example:
Every SQL statement begins with a verb, a keyword that describes what the statement
does. CREATE, INSERT, and DELETE are typical verbs. The statement continues with
one or more clauses. A clause may specify the data to be acted upon by the statement, or
provide more detail about what the statement is supposed to do.
Every clause also begins with a keyword, such as WHERE, FROM, INTO, and HAVING.
Some clauses are optional; others are required.

2.3. SQL key words
The SQL keywords are words that are reserved words that are not used as a user defined
data. The most commonly used SQL key words according to ANSI/ISO SQL keywords are
as follows:
ADA DEC GRANT NUMERIC

ALL DECIMAL GROUP OF
AND DECLARE HAVING ON
ANY DEFUALT IN OPEN
AS DELETE INDICATOR OPTION
ASC DESC INSERT OPEN
AUTHORIZATION DISTNICT INT OPTION
AVG DOUBLE INTEGER OR
BEGIN END INTO ORDER
BETWEEN ESCAPE IS PRIMARY
BY EXEC KEY REAL
C EXISTS LANGAUGE SELECT
CHAR FETCH LIKE SET
CHARACTER FLOAT MAX SOME
CHECK FOR MIN SUM
CLOSE FOREIGN MODULE TABLE
COBOL FORTRAN NOT TO UNION
COMMIT FOUND NULL UPDATE
CONTINUE FROM USER
COUNT GO VIEW
CREATE GOTO WHERE
CURRENT WITH
CURSOR WORK

2.4. Name
The objects in a SQL-based database are identified by assigning them unique names.
Names are used in SQL statements to identify the database object on which the statement
should act.
The ANSI/ISO SQL standard specifies tables names(which identify tables), column names
(which identify columns), and user names (which identify users of the database)
The SQL database Name should not be empty and special characters. The ANSI/ISO
standards specifies that SQL names must contain 1 to 18 characters, begin with a letter,
and my not contain any spaces or special punctuation characters.
2.4.1. Table Name

When you specify a table name in a SQL statement, SQL assumes that you are referring to
one of your own tables (that is, a table that you created). With the proper permission, you
can also refer to tables owned by other users using a qualified table name.
2.4.2. Column Name

When you specify a column name in a SQL statement, SQL can normally determine from
the context which column you intend. A column name should not be blank and the same in
the same database.
2.5. Data Types

There is a standard that specifies various types of data that can be stored in a SQL-based
database and manipulated by the SQL languages.
Character strings:
Data type Description Storage
char(n) or Fixed-length character string. Maximum 8,000 characters n
character(n)
varchar(n) Variable-length character string. Maximum 8,000 characters
varchar(max) Variable-length character string. Maximum 1,073,741,824 characters
text Variable-length character string. Maximum 2GB of text data
Unicode strings:
nchar(n) Fixed-length Unicode data. Maximum 4,000 characters
nvarchar(n) Variable-length Unicode data. Maximum 4,000 characters
nvarchar(max) Variable-length Unicode data. Maximum 536,870,912
characters
ntext Variable-length Unicode data. Maximum 2GB of text data

Binary types:
bit Allows 0, 1, or NULL
binary(n) Fixed-length binary data. Maximum 8,000 bytes
varbinary(n) Variable-length binary data. Maximum 8,000 bytes
varbinary(max) Variable-length binary data. Maximum 2GB
image Variable-length binary data. Maximum 2GB
Number types:
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
decimal(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
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 types:
datetime From January 1, 1753 to December 31, 9999 with an accuracy of 8 bytes
3.33 milliseconds
datetime2 From January 1, 0001 and December 31, 9999 with an accuracy of 6-8
100 nanoseconds bytes
smalldatetime From January 1, 1900 to June 6, 2079 with an accuracy of 1 4 bytes
minute
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:
Data type Description
sql_variant Stores up to 8,000 bytes of data of various data types, except text, ntext,
and timestamp
uniqueidentifier Stores a globally unique identifier (GUID)
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
o Fixed-length character strings: columns holding these types of data typically store
names of people and companies, addresses, descriptions, and so on.
o Integers: columns holding this types of data typically store counts, quantities, ages, and
so on. Integer’s columns are also frequently used to contain Id numbers, such as
customers, employee. And order numbers.
o Decimal numbers: columns with this type store numbers that have fractional parts and
must be calculated exactly, such as rates and percentages. They are also frequently
used to store money amounts.
o Floating point numbers: columns with this types are used to store scientific numbers
which calculated and its values are estimated in powers of numbers. Example: weights,
and longer distances
2.5.1. Extended data Types
o Variable-length Character string: SQL which supports VARCHAT data. Which allows a
column to store character strings that vary in length from row to row, up to some
maximum length.

o Dates and times: supports for date/time values.
o Boolean data: supports logical(TRUE or FALSE) values as an explicit type.
2.5.2. Data Types Differences
The differences b/n the data types offered in various SQL implementation is one of the
practical barriers to the portability of SQL based applications.
Example: Date/time data provides an excellent example of theses differences.
Date: w/c stores a date like June 30, 2009 or 30 June 2009
2.6. Constants
In some SQL statements a numeric, character, or date data value must be expressed in
text form.
For example: INSERT statement, w/c adds a student to the database:
INSERT INTO student(Fname, SID, Dept, year)
VALUES (‘Alemayehu’, 200, ‘Comp Science’, 2)
The value for each column in the newly inserted row is specified in the VALUES clause.
Constant data values are also used in expression such as in the SELECT statement
SELECT city
FROM offices
WHERE TARGET >(1.1* SALES) +1000.00
2.6.1. Numeric constant

Integers and decimal constants (also called exact numeric literals) are written as ordinary
decimal numbers in SQL statements, with optional leading plus or minus sign
Example: 200 +345.95 -500 789.00
Use a comma between the digits of a numeric constant
2.6.2. String Constant
The ANSI/ISO standard specifies that SQL constants for character data be enclosed in
single quotes (‘……’)
Example: ‘Waksum Motuma’ ‘Addis Ababa’
If a single quotes is to be used included in the constant text, it is written within the constant
as two consecutive single quote characters. This is constant value:
Example: “I can’t”

2.6.3. Date and time constants
In SQL products supports date/time data. Constant values for dates, times, and time
intervals are specified as string constants. The format of these constants varies from one
DBMS to the next.
Example:
SELECT Name, dept
FROM student
WHERE hire-date= To-date(‘June 30, 2009’, ‘mon DD yyyy’)
2.7. Expressions
Expressions are used in the SQL Languages to calculate values that are retrieved from the
database and to calculate values used in searching the database.
Example1: The query that calculates sales of each offices as a percentage of its target:
SELECT city, target, sales,(sales/target)*100

FROM offices
Example2:
SELECT city
FROM offices
WHERE sales > target +50000.00
2.8. Missing data (Null Values)
It is a value whose value is missing, unknown, or don’t apply. SQL supports missing,
unknown, or inapplicable data explicitly through the concepts of null values. A null Value is
an indicator that tells SQL (and the user) that the data is missing or not applicable.
Example: given a student table below that has missing values

3. Starting SQL server
1. Click on Start button and point to All programs
2. Click on Microsoft SQL server 2005
3. Click on SQL Server Management Studio
4. Click on Connect button
4. SQL Commands
4.1. Create:-
4.1.1. Create SQL DB
The CREATE DATABASE Statement

The CREATE DATABASE statement is used to create a database.
SQL CREATE DATABASE Syntax
CREATE DATABASE database_name
CREATE DATABASE Example

Now we want to create a database called "my_db".
We use the following CREATE DATABASE statement:
CREATE DATABASE my_db
Database tables can be added with the CREATE TABLE statement.
4.1.2. SQL Table

The CREATE TABLE Statement
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.
 Below is an example of a table called "Persons":
P_Id LastName FirstName Address City
1 Aberu Ola AA Arada Subsity
2 Chala sanyi W/shoa Ambo
3 Mohammad Kari Arsi Asella
 The table above contains three records (one for each person) and five columns
(P_Id, LastName, FirstName, Address, and City).
The CREATE TABLE statement is used to create a table in a database.

SQL CREATE TABLE Syntax
CREATE TABLE table_name
(
column_name1 data_type,
....
)
CREATE TABLE Example
Now we want to create a table called "Persons" that contains five columns: P_Id,
LastName, FirstName, Address, and City.
We use the following CREATE TABLE statement:
CREATE TABLE Persons
(
P_Id int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)
The P_Id column is of type int and will hold a number. The LastName, FirstName, Address,
and City columns are of type varchar with a maximum length of 255 characters.
The empty "Persons" table will now look like this:
The empty table can be filled with data with the INSERT INTO statement.
4.2. SQL Constraints

Constraints are used to limit the type of data that can go into a table.
Constraints can be specified when a table is created (with the CREATE TABLE statement)
or after the table is created (with the ALTER TABLE statement).
We will focus on the following constraints:
 NOT NULL
 UNIQUE
 PRIMARY KEY
 FOREIGN KEY
 CHECK
 DEFAULT
4.2.1. SQL NOT NULL Constraint

By default, a table column can hold NULL values.
 The NOT NULL constraint enforces a column to NOT accept NULL values.
 The NOT NULL constraint enforces a field to always contain a value. This means
that you cannot insert a new record, or update a record without adding a value to
this field.

 The following SQL enforces the "P_Id" column and the "LastName" column to not
accept NULL values:
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
City varchar(255)
)
4.2.2. SQL UNIQUE Constraint

 The UNIQUE constraint uniquely identifies each record in a database table.
 The UNIQUE and PRIMARY KEY constraints both provide a guarantee for
uniqueness for a column or set of columns.
 A PRIMARY KEY constraint automatically has a UNIQUE constraint defined on it.
 Note that you can have 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 "P_Id" column when the "Persons"
table is created:
(
P_Id int NOT NULL UNIQUE,
City varchar(255)
)
To allow naming of a UNIQUE constraint, and for defining a UNIQUE constraint on multiple
columns, use the following SQL syntax:
(
P_Id int NOT NULL,
City varchar(255),
CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)
)
SQL UNIQUE Constraint on ALTER TABLE

To create a UNIQUE constraint on the "P_Id" column when the table is already created,
use the following SQL:
ALTER TABLE Persons
ADD UNIQUE (P_Id)

To allow naming of a UNIQUE constraint, and for defining a UNIQUE constraint on multiple
columns, use the following SQL syntax:
ALTER TABLE Persons
ADD CONSTRAINT uc_PersonID UNIQUE (P_Id,LastName)
To DROP a UNIQUE Constraint

ALTER TABLE Persons
DROP CONSTRAINT uc_PersonID
4.2.3. SQL PRIMARY KEY Constraint

 The PRIMARY KEY constraint uniquely identifies each record in a database table.
 Primary keys must contain unique values.
 A primary key column cannot contain NULL values.
 Each table should have a primary key.
SQL PRIMARY KEY Constraint on CREATE TABLE
The following SQL creates a PRIMARY KEY on the "P_Id" column when the "Persons"
table is created:
(
P_Id int NOT NULL PRIMARY KEY,
City varchar(255)
)
To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY
constraint on multiple columns, use the following SQL syntax:
(
P_Id int NOT NULL,
City varchar(255),
CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)
)
SQL PRIMARY KEY Constraint on ALTER TABLE

To create a PRIMARY KEY constraint on the "P_Id" column when the table is already
created, use the following SQL:
ALTER TABLE Persons
ADD PRIMARY KEY (P_Id)
To allow naming of a PRIMARY KEY constraint, and for defining a PRIMARY KEY
ALTER TABLE Persons
ADD CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName)

Note: If you use the ALTER TABLE statement to add a primary key, the primary key
column(s) must already have been declared to not contain NULL values (when the table
was first created).
To DROP a PRIMARY KEY Constraint
To drop a PRIMARY KEY constraint, use the following SQL:
ALTER TABLE Persons
DROP CONSTRAINT pk_PersonID
4.2.4. SQL FOREIGN KEY Constraint

 A FOREIGN KEY in one table points to a PRIMARY KEY in another table.
 Let's illustrate the foreign key with an example. Look at the following two tables:
The "Persons" table:
1 Hansen Ola Timoteivn 10 Sandnes
2 Svendson Tove Borgvn 23 Sandnes
3 Pettersen Kari Storgt 20 Stavanger
The "Orders" table:
O_Id OrderNo P_Id
1 77895 3
2 44678 3
3 22456 2
4 24562 1
Note that the "P_Id" column in the "Orders" table points to the "P_Id" column in the
"Persons" table.
 The "P_Id" column in "Persons" table is the PRIMARY KEY in the "Persons" table.
 The "P_Id" column in "Orders" table is a FOREIGN KEY in the "Orders" table.
 The FOREIGN KEY constraint is used to prevent actions that would destroy link
between tables.
 The FOREIGN KEY constraint also prevents that invalid data is inserted into the
foreign key column, because it has to be one of the values contained in the table it
points to.
SQL FOREIGN KEY Constraint on CREATE TABLE

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

(
O_Id int NOT NULL,
P_Id int,
PRIMARY KEY (O_Id),
CONSTRAINT fk_PerOrders FOREIGN KEY (P_Id)
REFERENCES Persons(P_Id)
)
SQL FOREIGN KEY Constraint on ALTER TABLE
To create a FOREIGN KEY constraint on the "P_Id" column when the "Orders" table is
already created, use the following SQL::
ALTER TABLE Orders
ADD FOREIGN KEY (P_Id)
To allow naming of a FOREIGN KEY constraint, and for defining a FOREIGN KEY
ALTER TABLE Orders
ADD CONSTRAINT fk_PerOrders
FOREIGN KEY (P_Id)
To DROP a FOREIGN KEY Constraint

To drop a FOREIGN KEY constraint, use the following SQL:
ALTER TABLE Orders
DROP CONSTRAINT fk_PerOrders
4.2.5. SQL DEFAULT Constraint

 The DEFAULT constraint is used to insert a default value into a column.
 The default value will be added to all new records, if no other value is specified.
SQL DEFAULT Constraint on CREATE TABLE
The following SQL creates a DEFAULT constraint on the "City" column when the "Persons"
table is created:
(
P_Id int NOT NULL,
City varchar(255) DEFAULT 'Sandnes'
)
The DEFAULT constraint can also be used to insert system values, by using functions like
GETDATE():

CREATE TABLE Orders
(
O_Id int NOT NULL,
P_Id int,
OrderDate date DEFAULT GETDATE()
)
SQL DEFAULT Constraint on ALTER TABLE

To create a DEFAULT constraint on the "City" column when the table is already created,
use the following SQL:
ALTER TABLE Persons
ALTER COLUMN City SET DEFAULT 'SANDNES'
To DROP a DEFAULT Constraint

To drop a DEFAULT constraint, use the following SQL:
ALTER TABLE Persons
ALTER COLUMN City DROP DEFAULT
4.3. SQL Statements

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. For most systems, every SQL statement is terminated by a semicolon (;).
 We are using MS Access and SQL Server 2000 and we do not have to put a
semicolon after each SQL statement, but some database programs force to use it.
 An SQL statement can be entered on one line or split across several lines for clarity.
 For most systems SQL is not case sensitive. We can mix uppercase and lowercase
when referencing SQL keywords (such as SELECT and INSERT), tables names,
and column names.
4.3.1. SQL INSERT INTO Statement

The INSERT INTO statement is used to insert new records in a table.
SQL INSERT INTO Syntax
It is possible to write the INSERT INTO statement in two forms.

The first form doesn't specify the column names where the data will be inserted, only their
values:
INSERT INTO table_name
VALUES (value1, value2, value3,...)
The second form specifies both the column names and the values to be inserted:
INSERT INTO table_name (column1, column2, column3,...)
VALUES (value1, value2, value3,...)
SQL INSERT INTO Example

Now we want to insert a new row in the "Persons" table.

INSERT INTO Persons
VALUES (4,'Nilsen', 'Johan', 'Bakken 2', 'Stavanger')
The "Persons" table will now look like this:

4 Nilsen Johan Bakken 2 Stavanger
Insert Data Only in Specified Columns
It is also possible to only add data in specific columns.
The following SQL statement will add a new row, but only add data in the "P_Id",
"LastName" and the "FirstName" columns:
INSERT INTO Persons (P_Id, LastName, FirstName)
VALUES (5, 'Tjessem', 'Jakob')

5 Tjessem Jakob

4.3.2. SQL SELECT Statement
The SELECT statement is used to select data from a database.
The result is stored in a result table, called the result-set.
SQL SELECT Syntax
SELECT column_name(s)
FROM table_name
and
SELECT * FROM table_name
An SQL SELECT Example
The persons table:

Now we want to select the content of the columns named "LastName" and "FirstName"
from the table above.
We use the following SELECT statement:
SELECT LastName,FirstName FROM Persons
The result-set will look like this:
LastName FirstName
Hansen Ola
Svendson Tove
Pettersen Kari
SELECT * Example
Now we want to select all the columns from the "Persons" table.
SELECT * FROM Persons
Tip: The asterisk (*) is a quick way of selecting all columns!
Navigation in a Result-set
Most database software systems allow navigation in the result-set with programming
functions, like: Move-To-First-Record, Get-Record-Content, Move-To-Next-Record, etc.

4.3.2.1. SQL WHERE Clause
 The WHERE clause is used to filter records.
 The WHERE Clause
 The WHERE clause is used to extract only those records that fulfill a specified
criterion.
SQL WHERE Syntax
FROM table_name
WHERE column_name operator value
WHERE Clause Example

Now we want to select only the persons living in the city "Sandnes" from the table above.
WHERE City='Sandnes'
Quotes Around Text Fields
SQL uses single quotes around text values (most database systems will also accept double
quotes). Although, numeric values should not be enclosed in quotes.
For text values:
This is correct:
SELECT * FROM Persons WHERE FirstName='Tove'
This is wrong:
SELECT * FROM Persons WHERE FirstName=Tove
For numeric values:
This is correct:
SELECT * FROM Persons WHERE Year=1965
This is wrong:
SELECT * FROM Persons WHERE Year='1965'

A. Operators Allowed in the WHERE Clause
With the WHERE clause, the following operators can be used:
Operator Description
= Equal
<> Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
IN If you know the exact value you want to return for at least one of
the columns
Note: In some versions of SQL the <> operator may be written as !=
B. SQL AND & OR Operators

 AND & OR operators are used to filter records based on more than one condition.
 AND operator displays a record if both the first and the second condition is true.
 OR operator displays a record if either the first or the second condition is true.
AND Operator Example
Now we want to select only the persons with the first name equal to "Tove" AND the last
name equal to "Svendson":
WHERE FirstName='Tove'
AND LastName='Svendson'
OR Operator Example
Now we want to select only the persons with the first name equal to "Tove" OR the first
name equal to "Ola":
WHERE FirstName='Tove'
OR FirstName='Ola'

C. Combining AND & OR
You can also combine AND and OR (use parenthesis to form complex expressions).
Now we want to select only the persons with the last name equal to "Svendson" AND the
first name equal to "Tove" OR to "Ola":
SELECT * FROM Persons WHERE
LastName='Svendson'
AND (FirstName='Tove' OR FirstName='Ola')
4.3.3. SQL ORDER BY Keyword

 The ORDER BY keyword is used to sort the result-set.
 The ORDER BY keyword is used to sort the result-set by a specified column.
 The ORDER BY keyword sort the records in ascending order by default.
 If you want to sort the records in a descending order, you can use the DESC
keyword.
SQL ORDER BY Syntax
FROM table_name
ORDER BY column_name(s) ASC|DESC
ORDER BY Example
4 Nilsen Tom Vingvn 23 Stavanger
Now we want to select all the persons from the table above, however, we want to sort the
persons by their last name.
ORDER BY LastName

ORDER BY DESC Example
Now we want to select all the persons from the table above, however, we want to sort the
persons descending by their last name.
ORDER BY LastName DESC
4.3.4. SQL UPDATE Statement

The UPDATE statement is used to update existing records in a table.
SQL UPDATE Syntax
UPDATE table_name
SET column1=value, column2=value2,...
WHERE some_column=some_value
Note: Notice the WHERE clause in the UPDATE syntax. The WHERE clause specifies
which record or records that should be updated. If you omit the WHERE clause, all records
will be updated!
SQL UPDATE Example
5 Tjessem Jakob
Now we want to update the person "Tjessem, Jakob" in the "Persons" table.
UPDATE Persons
SET Address='Nissestien 67', City='Sandnes'
WHERE LastName='Tjessem' AND FirstName='Jakob'
5 Tjessem Jakob Nissestien 67 Sandnes

SQL UPDATE Warning
Be careful when updating records. If we had omitted the WHERE clause in the example
above, like this:
UPDATE Persons
SET Address='Nissestien 67', City='Sandnes'
The "Persons" table would have looked like this:
1 Hansen Ola Nissestien 67 Sandnes
2 Svendson Tove Nissestien 67 Sandnes
3 Pettersen Kari Nissestien 67 Sandnes
4 Nilsen Johan Nissestien 67 Sandnes
4.3.5. SQL DELETE Statement

The DELETE statement is used to delete records/ rows in a table.
SQL DELETE Syntax
DELETE FROM table_name
WHERE some_column=some_value
Note: Notice the WHERE clause in the DELETE syntax. The WHERE clause specifies
which record or records that should be deleted. If you omit the WHERE clause, all records
will be deleted!
SQL DELETE Example
Now we want to delete the person "Tjessem, Jakob" in the "Persons" table.
DELETE FROM Persons
WHERE LastName='Tjessem' AND FirstName='Jakob'

Delete All Rows
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
or
DELETE * FROM table_name
Note: Be very careful when deleting records. You cannot undo this statement!
4.3.6. The DROP TABLE Statement

The DROP TABLE statement is used to delete a table.
DROP TABLE table_name
4.3.7. The DROP DATABASE Statement

The DROP DATABASE statement is used to delete a database.
DROP DATABASE database_name
4.3.8. The TRUNCATE TABLE Statement

What if we only want to delete the data inside the table, and not the table itself?
Then, use the TRUNCATE TABLE statement:
TRUNCATE TABLE table_name
4.3.9. SQL ALTER TABLE Statement

The ALTER TABLE statement is used to add, delete or modify columns in an existing table.
SQL ALTER TABLE Syntax
To add a column in a table, use the following syntax:
ALTER TABLE table_name
ADD column_name datatype
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
To change the data type of a column in a table, use the following syntax:
ALTER COLUMN column_name datatype

SQL ALTER TABLE Example
Look at the "Persons" table:
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.
The "Persons" table will now like this:
P_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. We use the following SQL statement:
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-digit 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 like this:

4.3.10. SQL AUTO INCREMENT Field
Auto-increment allows a unique number to be generated when a new record is
inserted into a table.
AUTO INCREMENT a Field
Very often we would like the value of the primary key field to be created automatically every
time a new record is inserted.
We would like to create an auto-increment field in a table.
Syntax for SQL Server
The following SQL statement defines the "P_Id" column to be an auto-increment primary
key field in the "Persons" table:
(
P_Id int PRIMARY KEY IDENTITY,
City varchar(255)
)
The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature.
By default, the starting value for IDENTITY is 1, and it will increment by 1 for each new
record.
To specify that the "P_Id" column should start at value 10 and increment by 5, change the
identity to IDENTITY(10,5).
To insert a new record into the "Persons" table, we will not have to specify a value for the
"P_Id" 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 "P_Id"
column would be assigned a unique value. The "FirstName" column would be set to "Lars"
and the "LastName" column would be set to "Monsen".

5. SQL Functions
5.1. Overview of SQL Functions
SQL has many built-in functions for performing calculations on data.
SQL Aggregate Functions
SQL aggregate functions return a single value, calculated from values in a column.
Useful aggregate functions:
AVG() - Returns the average value
 COUNT() - Returns the number of rows
 FIRST() - Returns the first value
 LAST() - Returns the last value
 MAX() - Returns the largest value
 MIN() - Returns the smallest value
 SUM() - Returns the sum
SQL Scalar functions
SQL scalar functions return a single value, based on the input value.
Useful scalar functions:
 UPPER() - Converts a field to upper case
 LCASE() - Converts a field to lower case
 MID() - Extract characters from a text field
 LEN() - Returns the length of a text field
 ROUND() - Rounds a numeric field to the number of decimals specified
 NOW() - Returns the current system date and time
 FORMAT() - Formats how a field is to be displayed
Tip: The aggregate functions and the scalar functions will be explained in details in the next
chapters.
5.1.1. SQL AVG() Function
The AVG() function returns the average value of a numeric column.
SQL AVG() Syntax
SELECT AVG(column_name) FROM table_name
SQL AVG() Example
We have the following "Orders" table:
O_Id OrderDate OrderPrice Customer
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen

Now we want to find the average value of the "OrderPrice" fields.
SELECT AVG(OrderPrice) AS OrderAverage FROM Orders
OrderAverage
950
Now we want to find the customers that have an OrderPrice value higher then the average
OrderPrice value.
SELECT Customer FROM Orders
WHERE OrderPrice>(SELECT AVG(OrderPrice) FROM Orders)
Customer
Hansen
Nilsen
Jensen
5.1.2. SQL COUNT() Function

The COUNT() function returns the number of rows that matches a specified criteria.
SQL COUNT(column_name) Syntax
The COUNT(column_name) function returns the number of values (NULL values will not be
counted) of the specified column:
SELECT COUNT(column_name) FROM table_name
SQL COUNT(*) Syntax

The COUNT(*) function returns the number of records in a table:
SELECT COUNT(*) FROM table_name
SQL COUNT(DISTINCT column_name) Syntax

The COUNT(DISTINCT column_name) function returns the number of distinct values of the
specified column:
SELECT COUNT(DISTINCT column_name) FROM table_name
Note: COUNT(DISTINCT) works with ORACLE and Microsoft SQL Server, but not with
Microsoft Access.

SQL COUNT(column_name) Example
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to count the number of orders from "Customer Nilsen".
SELECT COUNT(Customer) AS CustomerNilsen FROM Orders
WHERE Customer='Nilsen'
The result of the SQL statement above will be 2, because the customer Nilsen has made 2
orders in total:
CustomerNilsen
2
SQL COUNT(*) Example
If we omit the WHERE clause, like this:
SELECT COUNT(*) AS NumberOfOrders FROM Orders
NumberOfOrders
6
which is the total number of rows in the table.
SQL COUNT(DISTINCT column_name) Example
Now we want to count the number of unique customers in the "Orders" table.
SELECT COUNT(DISTINCT Customer) AS NumberOfCustomers FROM
Orders

NumberOfCustomers
which is the number of unique customers (Hansen, Nilsen, and Jensen) in the "Orders"
table.

5.1.3. SQL UPPER() Function
The UPPER() function converts the value of a field to uppercase.
SQL UPPER() Syntax
SELECT UPPER(column_name) FROM table_name
SQL UPPER() Example
We have the following "Persons" table:
Now we want to select the content of the "LastName" and "FirstName" columns above,
and convert the "LastName" column to uppercase.
SELECT UPPER(LastName) as LastName,FirstName FROM
Persons
LastName FirstName
HANSEN Ola
SVENDSON Tove
PETTERSEN Kari
5.1.4. SQL FIRST() Function

The FIRST() function returns the first value of the selected column.
SQL FIRST() Syntax
SELECT FIRST(column_name) FROM table_name
SQL FIRST() Example
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to find the first value of the "OrderPrice" column.

SELECT FIRST(OrderPrice) AS FirstOrderPrice FROM Orders
FirstOrderPrice
1000
5.1.5. SQL LAST() Function

The LAST() function returns the last value of the selected column.
SQL LAST() Syntax
SELECT LAST(column_name) FROM table_name
SQL LAST() Example
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to find the last value of the "OrderPrice" column.
SELECT LAST(OrderPrice) AS LastOrderPrice FROM Orders
LastOrderPrice
100
5.1.6. SQL MAX() Function

The MAX() function returns the largest value of the selected column.
SQL MAX() Syntax
SELECT MAX(column_name) FROM table_name
SQL MAX() Example
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen

Now we want to find the largest value of the "OrderPrice" column.
SELECT MAX(OrderPrice) AS LargestOrderPrice FROM Orders
LargestOrderPrice
2000
5.1.7. SQL MIN() Function

The MIN() function returns the smallest value of the selected column.
SQL MIN() Syntax
SELECT MIN(column_name) FROM table_name
SQL MIN() Example

1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to find the smallest value of the "OrderPrice" column.
SELECT MIN(OrderPrice) AS SmallestOrderPrice FROM Orders
SmallestOrderPrice
100
5.1.8. SQL SUM() Function

The SUM() Function
The SUM() function returns the total sum of a numeric column.
SQL SUM() Syntax
SELECT SUM(column_name) FROM table_name

SQL SUM() Example
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to find the sum of all "OrderPrice" fields".
SELECT SUM(OrderPrice) AS OrderTotal FROM Orders
OrderTotal
5700
5.2. SQL GROUP BY Statement
The GROUP BY statement is used in conjunction with the aggregate functions to group the
result-set by one or more columns.
SQL GROUP BY Syntax
SELECT column_name, aggregate_function(column_name)
FROM table_name
GROUP BY column_name
SQL GROUP BY Example
1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to find the total sum (total order) of each customer.
We will have to use the GROUP BY statement to group the customers.
SELECT Customer,SUM(OrderPrice) FROM Orders
GROUP BY Customer

Customer SUM(OrderPrice)
Hansen 2000
Nilsen 1700
Jensen 2000
Let's see what happens if we omit the GROUP BY statement:
Hansen 5700
Nilsen 5700
Hansen 5700
Hansen 5700
Jensen 5700
Nilsen 5700
The result-set above is not what we wanted.
Explanation of why the above SELECT statement cannot be used: The SELECT
statement above has two columns specified (Customer and SUM(OrderPrice). The
"SUM(OrderPrice)" returns a single value (that is the total sum of the "OrderPrice" column),
while "Customer" returns 6 values (one value for each row in the "Orders" table). This will
therefore not give us the correct result. However, you have seen that the GROUP BY
statement solves this problem.
GROUP BY More Than One Column
We can also use the GROUP BY statement on more than one column, like this:
SELECT Customer,OrderDate,SUM(OrderPrice) FROM Orders
GROUP BY Customer,OrderDate
5.2.1. SQL HAVING Clause

The HAVING clause was added to SQL because the WHERE keyword could not be used
with aggregate functions.
SQL HAVING Syntax
SELECT column_name, aggregate_function(column_name)
FROM table_name
GROUP BY column_name
HAVING aggregate_function(column_name) operator value
SQL HAVING Example

1 2008/11/12 1000 Hansen
2 2008/10/23 1600 Nilsen
3 2008/09/02 700 Hansen
4 2008/09/03 300 Hansen
5 2008/08/30 2000 Jensen
6 2008/10/04 100 Nilsen
Now we want to find if any of the customers have a total order of less than 2000.
GROUP BY Customer
HAVING SUM(OrderPrice)<2000
Nilsen 1700
Now we want to find if the customers "Hansen" or "Jensen" have a total order of more than
1500.
We add an ordinary WHERE clause to the SQL statement:
WHERE Customer='Hansen' OR Customer='Jensen'
GROUP BY Customer
HAVING SUM(OrderPrice)>1500

Hansen 2000
Jensen 2000

Reference
1. Fundamentals of Relational Database Design
2. Fundamentals of SQL server 2005
3. Basic SQL reference
4. www.Microsoft .com

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1.

1.1. Overview of SQL

 SQL stands for Structured Query Language

1.2. History of SQL

1.3. Function of SQL

 SQL can retrieve data from a database

Structured Query Language 1

1.4. SQL Components

1. Data Manipulation Language (DML), which retrieves or modifies data

1.4.1. SQL DML

Structured Query Language 2

1. CREATE DATABASE - creates a new database

6. CREATE INDEX - creates an index (search key)

Changes to the structure of a database are handled by a different set of SQL

Structured Query Language 3

Structured Query Language 4

2.2 Introduction to SQL Statement/ commands

Structured Query Language 5

REVOKE Removes user access privileges

Structured Query Language 6

ADA DEC GRANT NUMERIC

Structured Query Language 7

2.4.1. Table Name

2.4.2. Column Name

2.5. Data Types

Structured Query Language 8

The p parameter indicates the maximum total number of digits that

The s parameter indicates the maximum number of digits stored to

Structured Query Language 9

Structured Query Language 10

2.6.1. Numeric constant

Structured Query Language 11

SELECT city, target, sales,(sales/target)*100

2.8. Missing data (Null Values)

Example: given a student table below that has missing values

Structured Query Language 12

The CREATE DATABASE Statement

CREATE DATABASE Example

Database tables can be added with the CREATE TABLE statement.

4.1.2. SQL Table

Structured Query Language 13

4.2. SQL Constraints

4.2.1. SQL NOT NULL Constraint

Structured Query Language 14

4.2.2. SQL UNIQUE Constraint

SQL UNIQUE Constraint on CREATE TABLE

SQL UNIQUE Constraint on ALTER TABLE

Structured Query Language 15

To DROP a UNIQUE Constraint

4.2.3. SQL PRIMARY KEY Constraint

SQL PRIMARY KEY Constraint on ALTER TABLE

Structured Query Language 16

4.2.4. SQL FOREIGN KEY Constraint

SQL FOREIGN KEY Constraint on CREATE TABLE

Structured Query Language 17

SQL FOREIGN KEY Constraint on ALTER TABLE

To DROP a FOREIGN KEY Constraint

4.2.5. SQL DEFAULT Constraint