Wachemo University Information Technology Program.

Fundamentals of Database System

Chapter One
Introduction
Overview
Database systems are designed to manage large data set in an organization. The data
management involves both definition and the manipulation of the data which ranges from simple
representation of the data to considerations of structures for the storage of information. The data
management also considers the provision of mechanisms for the manipulation of information.

Today, Databases are essential to every business. They are used to maintain internal records, to
present data to customers and clients on the World-Wide-Web, and to support many other
commercial processes. Databases are likewise found at the core of many modern organizations.

The power of databases comes from a body of knowledge and technology that has developed
over several decades and is embodied in specialized software called a database management
system, or DBMS. A DBMS is a powerful tool for creating and managing large amounts of data
efficiently and allowing it to persist over long periods of time, safely. These systems are among
the most complex types of software available.

Thus, for our question: What is a database? In essence a database is nothing more than a
collection of shared information that exists over a long period of time, often many years. In
common dialect, the term database refers to a collection of data that is managed by a DBMS.

Thus the DB course is about:

􀂄 How to organize data

􀂄 supporting multiple users
􀂄 Efficient and effective data retrieval
􀂄 Secured and reliable storage of data
􀂄 maintaining consistent data
􀂄 making information useful for decision making
Basics of Database

Definition

Databases have been defined differently in literature.

 A shared collection of logically related data, designed to meet the information needs of
multiple users in an organization.
 A collection of related information about a subject organized in a useful manner that
provides a base or foundation for procedures such as retrieving information, drawing
conclusions, and making decisions.
 An organized collection of information in computerized format.

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 A collection of data: part numbers, product codes, customer information, etc. It usually
refers to data organized and stored on a computer that can be searched and retrieved by a
computer program called database management system.

The database management system (DBMS), on the other hand is the software or tool that is used
to manage the database and its users. It is a software system that enables users to define,
maintain and control access to the database.
In many books and may be in this course sometimes database and database management system
are used interchangeably but there is a clear difference and we should be clear about them. So
database is collection of data, DBMS is tool to manage this data, and both jointly are called
database system.
Databases are important; why? Traditionally computer applications are divided into commercial
and scientific (or engineering) ones. Scientific applications involve more computations, that is,
different type of calculations that vary from simple to very complex.

Today such applications exist, like in the fields of space, nuclear, medicine that take hours or
days of computations on even computers of the modern age. On the other hand, the applications
that are termed as commercial or business applications do not involve much computations, rather
minor computation but mainly they perform the input/output operations. That is, these
applications mainly store the data in the computer storage, then access and present it to the users
in different formats (also termed as data processing) for example, banks, shopping, production,
utilities billing, customer services and many others. As is clear from the example systems
mentioned, the commercial applications exist in the day to day life and are related directly with
the lives of common people. In order to manage the commercial applications more efficiently
databases are the ultimate choice because efficient management of data is the sole objective of
the databases. So such applications are being managed by databases even in a developing
country like Pakistan, yet to talk about the developed countries. This way databases are related
directly or indirectly almost every person in society. Databases are not only being used in the
commercial applications rather today many of the scientific/engineering application are also
using databases.
Traditional file based approach Vs. Database approach

A. File based approach

After the introduction of Computer for data processing to the business community, the need to
use the device for data storage and processing increase. There were, and still are, several
computer applications with file based processing used for the purpose of data handling. Even
though the approach evolved over time, the basic structure is still similar if not identical.

 This approach is the decentralized computerized data handling method.

 Focus was on applications for which programs would be written.
 All the data required would be stored in a file or files owned by the programs.

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 Each program was responsible for only its own data.

 A program would not be able to access another program’s files because different
programs could be written in different languages and the program needs to know the file
structure before it can access it.
 File base system is a collection of application programs perform services for the end-
users. In such systems, every application program that provides service to end users
define and manage its own data
 Such systems have number of programs for each of the different applications in the
organization.
 Since every application defines and manages its own data, the system is subjected to
serious data duplication problem.
 File, in file based approach, is a collection of records which contains logically related
data.

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Limitations of the Traditional File Based approach

 Separation or Isolation of Data:

 Available information in one application may not be known.
 Limited data sharing
 Lengthy development and maintenance time
 Duplication or redundancy of data
 Costs time and money to enter and maintain data
 Takes up additional storage capacity
 More importantly, redundancy leads to loss of data integrity(inconsistent data)
 Incompatible file formats between different applications and programs creating
inconsistency.
 Programs are written in different languages, and so cannot easily access each other’s
files.
 Fixed query processing which is defined during application development
The limitations for the traditional file based data handling approach arise from two basic reasons.
1. Definition of the data is embedded in the application program which makes it
difficult to modify the database definition easily.
2. No control over the access and manipulation of the data beyond that imposed by the
application programs.
Results: Database and database management systems

B. Database based approach

Database is a shared collection of logically related data (and description of this data), designed
to meet the information needs of an organization.

 Shared collection – can be used simultaneously by many departments and users.

 Logically related - comprise the important objects and the relationships between these
objects.
 Description of the data – the system catalogue (meta-data) provides description of data to
enable data independence.

Database Management System (DBMS) – is a software system that enables users to define,
create, and maintain the database and that provides controlled access to this database. It is a
general-purpose software system that facilitates the processes of defining, constructing,
manipulating, and sharing databases among various users and applications.
 Defining: a database involves specifying the data types, structures, and constraints of the
data to be stored in the database. The database definition or descriptive information is
also stored by the DBMS in the form of a database catalog or dictionary; it is called
meta-data.
 Constructing: the database is the process of storing the data on some storage medium
that is controlled by the DBMS .

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 Manipulating: a database includes functions such as querying the database to retrieve specific data,
updating the database to reflect changes in the miniworld, and generating reports from the data.
 Sharing a database allows multiple users and programs to access the database simultaneously.

Application program—An application program accesses the database by sending queries or requests
for data to the DBMS.
Database system – is the DBMS together with the database, including some application
programs.

Characteristics of Database approach

 Self-describing nature of database systems

 The database system contains
 Database
 Complete definition of the database structure and constraints(meta-data)
 Data abstraction
 Program-data independence – possible to change the data structure without
affecting the program
 Users view conceptual representation of data

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Benefits of the database approach

􀂾 Data can be shared: two or more users can access and use same data instead of storing
data in redundant manner for each user.

􀂾 Improved accessibility of data: by using structured query languages, the users can easily
access data without programming experience.

􀂾 Redundancy can be reduced: isolated data is integrated in database to decrease the

redundant data stored at different applications.

􀂾 Quality data can be maintained: the different integrity constraints in the database approach
will maintain the quality leading to better decision making.

􀂾 Inconsistency can be avoided: controlled data redundancy will avoid inconsistency of the
data in the database to some extent.

􀂾 Transaction support can be provided: basic demands of any transaction support systems
are implanted in a full scale DBMS.

􀂾 Integrity can be maintained: data at different applications will be integrated together with
additional constraints to facilitate shared data resource.

􀂾 Security majors can be enforced: the shared data can be secured by having different levels
of clearance and other data security mechanisms.

􀂾 Improved decision support: the database will provide information useful for decision
making.

􀂾 Standards can be enforced: the different ways of using and dealing with data by different
unite of an organization can be balanced and standardized by using database approach.

􀂾 Compactness: since it is an electronic data handling method, the data is stored compactly
(no voluminous papers).

􀂾 Speed: data storage and retrieval is fast as it will be using the modern fast computer
systems.

􀂾 Less labour: unlike the other data handling methods, data maintenance will not demand
much resource.

􀂾 Centralized information control: since relevant data in the organization will be stored at
one repository, it can be controlled and managed at the central level.

Limitations and risk of Database Approach

 Introduction of new professional and specialized personnel

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 Complexity in designing and managing data

 The cost and risk during conversion from the old to the new system
 High cost to be incurred to develop and maintain the system
 Complex backup and recovery services from the user’s perspective
 Reduced performance due to centralization and data independency
 High impact on the system when failure occurs to the central system

Users of Database Systems

 Application Programmers
 End Users
 Database administrators
Application programmers:

This category of database users contains those people who create different types of database
application programs. Application programmers design the application according to the needs of
the other users of the database in a certain environment. Application programmers are skilled
people who have clear idea of the structure of the database and know clearly about the needs of
the organizations.
End users:
These are workers, whose job requires accessing the database frequently for various purposes. This
group of users contains the people who use the database application programs developed by the
Application programmers.
This category further contains three types of users
 Naïve Users
 Sophisticated Users
 Casual Users
Naïve Users
This category of users simply uses the application database programs created by the
programmers. This group has no interaction with other parts of their database and only use the
programs meant for them. They have not to worry about the further working of the database.
􀂾 Sizable proportion of users
􀂾 Unaware of the DBMS
􀂾 only access the database based on their access level and demand
􀂾 Use standard and pre-specified types of queries

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Sophisticated Users:
This type of users has some additional rights over the Naïve users, which means that they can
access the data stored in the database any of their desired way. They can access data using the
application programs as well as other ways of accessing data. Although this type of users has
more rights to access data, but these users have to take more responsibility and they need to be
aware of the database structure. Moreover such users should be skilled enough to be able to get
data from database with making and damage or loss to the data in database.
􀂾 Are users familiar with the structure of the Database and facilities of the DBMS
􀂾 Have complex requirements
􀂾 Have higher level queries
􀂾 Are most of the time engineers, scientists, business analysts,

Casual Users:
􀂾 Users who access the database occasionally
􀂾 Need different information from the database each time
􀂾 Use sophisticated database queries to satisfy their needs
􀂾 Are most of the time middle to high level managers

Database Administrators (DBA):

This class of database users is the most technical class of db users. They need to have the
knowledge of how to design and manage the database use as well as to manage the data in the
database. DBA is a very responsible position in an organization. He is responsible for proper
working of the database and DBMS, has the responsibility of making proper database backups
and make necessary actions for recovering the database in case of a database crash. To fulfill the
requirements of a DBA position a DBA needs vast experience and very elegant technical skills.
􀂾 Responsible to oversee, control and manage the database resources (the database itself, the
DBMS and other related software)
􀂾 Authorizing access to the database
􀂾 Coordinating and monitoring the use of the database
􀂾 Responsible for determining and acquiring hardware and software resources
􀂾 Accountable for problems like poor security, poor performance of the system

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