Chapter 1

Introduction to Databases

Thomas Connolly, Carolyn Begg, Database System, A Practical Approach to Design Implementation and

Management, 4th Edition, Addison Wesley

Pg 3 ~ 26

Learning Outcomes

• Introduction

• Traditional File-based Systems

• Database Approach

• Roles in the Database Environment

• Advantages & Disadvantages of DBMS

Examples of Database Application

• Purchases from the supermarket

• Purchases using credit card

• Booking a holiday at the travel

• Using the local library

• Taking out insurance

• Using the Internet

• Studying at university

File-based Definition

• Collection of application program that perform services for the end users (e.g reports)

• Program defines and manages it’s own data

File-based Processing

Limitations of File-based

• Separation and isolation

• Duplication

• Program & data dependence

• Fixed queries

• Proliferation of application programs

Database

• Definition– A collection of self-describing and integrated

data files

• System catalog– Meta data– Data dictionary– Overhead data

• Data abstraction

Database Approach

• Data definition language (DDL)• Data manipulation language (DML)• Structured query language (SQL)• Security system• Integrity system• Concurrency control system• Backup & recovery system• View mechanism

Database Management System (DBMS)

DBMS Environment• Hardware

– Client-server architecture• Software

– dbms, os, network, application• Data

– Schema, subschema, table, attribute• People

– Data administrator & database administrator– Database designer: logical & physical– Application programmer– End-user: naive & sophisticated

• Procedure– Start, stop, log on, log off, back up, recovery

Roles in the Database Environment

• Data Administrator (DA)– Management of data resources

– Ensure database development support corporate objectives

• Database Administrator (DBA)– Physical realization of database

– More technically oriented

• Database Designers – Logical

• Identifying data

– Physical• Realization of logical database

• Application Programmers– Implement application program for user

• End Users (Naïve and Sophisticated)

Advantages of DBMS

• Control redundancy

• Consistency

• Integrity

• Security

• Concurrency control

• Backup & recovery

• Data standard

• More information

• Data sharing & conflict control

• Productivity & accessibility

• Economy of scale

• Maintenance

Limitations of DBMS

• Complexity• Size• Cost

– Software– Hardware– Conversion

• Performance• Vulnerability