Chapter 1 - Objectives

Some common uses of database systems.

Chapter 1 Characteristics of file-based systems.
Problems with file-based approach.
Meaning of the term database.
Meaning of the term Database
Management System (DBMS).
Introduction to Databases

Pearson Education © 2014 Pearson Education © 2014

Chapter 1 - Objectives Examples of Database Applications

Typical functions of a DBMS. Purchases from the supermarket
Major components of the DBMS Purchases using your credit card
environment. Booking a holiday at the travel agents
Personnel involved in the DBMS Using the local library
environment. Taking out insurance
History of the development of DBMSs. Renting a video
Advantages and disadvantages of DBMSs. Using the Internet
Studying at university

Pearson Education © 2014 Pearson Education © 2014

File-Based Systems File-Based Processing

Collection of application programs that

perform services for the end users (e.g.
reports).
Each program defines and manages its
own data.

Pearson Education © 2014 Pearson Education © 2014

Limitations of File-Based Approach Limitations of File-Based Approach

Separation and isolation of data Data dependence

Each program maintains its own set of data. File structure is defined in the program
Users of one program may be unaware of code.
potentially useful data held by other programs.
Incompatible file formats
Programs are written in different languages,
Duplication of data and so cannot easily access each other’s files.
Same data is held by different programs.
Wasted space and potentially different values Fixed Queries/Proliferation of application
and/or different formats for the same item. programs
Programs are written to satisfy particular
functions.
Any new requirement needs a new program.
Pearson Education © 2014 Pearson Education © 2014

Database Approach Database

Arose because: Shared collection of logically related data
Definition of data was embedded in (and a description of this data), designed to
application programs, rather than being meet the information needs of an
stored separately and independently. organization.
No control over access and manipulation of
data beyond that imposed by application System catalog (metadata) provides
programs.
description of data to enable program–data
Result: independence.
the database and Database Management
System (DBMS). Logically related data comprises entities,
attributes, and relationships of an
organization’s information.
Pearson Education © 2014 Pearson Education © 2014

Database Management System (DBMS) Database Management System (DBMS)

A software system that enables users to

define, create, maintain, and control
access to the database.

(Database) application program: a

computer program that interacts with
database by issuing an appropriate
request (SQL statement) to the DBMS.

Pearson Education © 2014 Pearson Education © 2014

Database Approach Database Approach

Data definition language (DDL). Controlled access to database may

Permits specification of data types, include:
structures and any data constraints. a security system
All specifications are stored in the database. an integrity system
a concurrency control system
Data manipulation language (DML). a recovery control system
General enquiry facility (query language) of a user-accessible catalog.
the data.

Pearson Education © 2014 Pearson Education © 2014

Views Views - Benefits

Allows each user to have his or her own Reduce complexity

view of the database. Provide a level of security
Provide a mechanism to customize the
A view is essentially some subset of the appearance of the database
database. Present a consistent, unchanging picture
of the structure of the database, even if
the underlying database is changed

Pearson Education © 2014 Pearson Education © 2014

Components of DBMS Environment Components of DBMS Environment

Hardware
Can range from a PC to a network of
computers.
Software
DBMS, operating system, network software (if
necessary) and also the application programs.
Data
Used by the organization and a description
of this data called the schema.

Pearson Education © 2014 Pearson Education © 2014

Components of DBMS Environment Roles in the Database Environment

Procedures Data Administrator (DA)

Instructions and rules that should be applied to Database Administrator (DBA)
the design and use of the database and DBMS.
People Database Designers (Logical and
Physical)
Application Programmers
End Users (naive and sophisticated)

Pearson Education © 2014 Pearson Education © 2014

History of Database Systems Advantages of DBMSs

First-generation Control of data redundancy

Hierarchical and Network Data consistency
More information from the same amount
Second generation of data
Relational Sharing of data
Improved data integrity
Third generation Improved security
Object-Relational
Object-Oriented
Enforcement of standards
Economy of scale

Pearson Education © 2014 Pearson Education © 2014

Advantages of DBMSs Disadvantages of DBMSs

Balance conflicting requirements Complexity

Improved data accessibility and Size
responsiveness Cost of DBMS
Increased productivity Additional hardware costs
Improved maintenance through data Cost of conversion
independence Performance
Increased concurrency Higher impact of a failure
Improved backup and recovery services

Pearson Education © 2014 Pearson Education © 2014