IT2301 Database Management Systems dbmsict'cmb'ac'lk

1
PREPARING FOR THE BIT
IT2301Database Management Systemsdbms_at_ict.cmb.ac
.lk
Preparing for BIT 03/05/2001
2
Todays Agenda

• Two Modules for Semester 2
• Database Management Systems
• Fundamentals of Software Engineering

3
BRIEF SYLLABUS

• TOPIC MIN.
  NO. OF HOURS
• 1. File Organisation ... 12
• 2. Introduction to DBMS 06
• 3. Data Model 04
• 4. Database Design Process 11
• 5. Data Normalisation process ... 03
• 6. Data Manipulation 24

4
BRIEF SYLLABUS cont.

• TOPIC MIN. NO. OF
  HOURS
• 2. Introduction to DBMS 06
• a. The Evolution of Database Technology 02
• b. Database Architecture 04

5
Introduction to DBMS - OBJECTIVES
AFTER SUCCESSFULLY COMPLETING THIS SECTION
STUDENTS SHOULD BE ABLE TO

• Define the following key terms Data,
  information, database, database system, database
  management system
• DATABASE - A collection of interrelated data
  items that can be processed by one or more
  application systems.

6
Introduction to DBMS - OBJECTIVES
AFTER SUCCESSFULLY COMPLETING THIS SECTION
STUDENTS SHOULD BE ABLE TO

• List and briefly describe components of a typical
  database environment
• Explain how four components hardware, software,
  data and people work together to form todays
  database systems.

7
Introduction to DBMS - OBJECTIVES
hardware, software, data and people
Computer Terminals Printer
DBMS Application Program
Database Data Dictionary/Directory
User Programmer/Analyst Administrator
8
Introduction to DBMS - OBJECTIVES cont.

• Discuss data sharing in an organisation between
  different functional areas, management levels and
  geographical locations

9
Introduction to DBMS - OBJECTIVES cont.

• Briefly describe the evolution of database systems

• Origins goes back to 1950s. Technology used for
  popular commercial data management products
• Conventional File Systems - flat file
• Hierarchical Data Model
• Network Data Model
• Relational Data Model

10
Introduction to DBMS - OBJECTIVES cont.

• Name several limitations of conventional file
  processing systems

• Program-data dependence
• Data redundancy
• Poor data control
• Inadequate data manipulation capabilities
• Excessive programming effort

11
Introduction to DBMS - OBJECTIVES cont.

• Explain advantages of the database approach,
  compared to traditional file processing

• Program-data independence
• Eliminate problems with data redundancy
• Flexibility
• Security
• Data Sharing and Availability

12
Traditional File Environment

• is a way of collecting and maintaining data in an
  organisation that leads to each functional area
  or division creating and maintaining its own data
  files and programs
• Payroll, Personnel, Benefit divisions maintaining
  their own data files and programs

13
Conventional File Systems

• File Processing
• using Procedural Languages (e.g. COBOL)
• Processing Methods
• Sequential in Batch Mode to Interactive
• Main Problems
• Application programs dependent on the
  organisation of the file
• Data Redundancy

14
a) Program-data dependence is the close
relationship between data stored in files and the
software programs that update and maintain those
files.
15
Program-data dependency ... Any change in data
organisation or format requires a change in all
the programs associated with those
files. e.g. Payroll dept. use a data file
containing information on employee names,
addresses and salaries.
16
Program-data dependency ...

• Personnel dept. decided to use this file after
  adding no. of children to the data for each
  employee.
• A program to update the file, adding the required
  data on the number of children for each employee,
  would have to be written
• Every program that accessed the data file would
  have to be rewritten so that each one could read
  the re-designed file.

17
b) Data Redundancy

• is the presence of duplicate data in multiple
  data files.
• Each department (Payroll, Personnel, Benefit)
  keep data on individual employees, in each of the
  department file.

• employee name, department, salary scale in
  Payroll file
• employee name, address, gender, date of birth,
  department, date of appointment in Personnel
  file
• employee name, address, insurance scheme, pension
  plan in Benefit file.

18
data files
Employee file Name, Address, NID number,
Designation
e.g. Personnel application program
data files
Payroll file Name, Address Hours worked, Pay rate
e.g. Payroll application program
data files
Benefit file Name, Address Insurance, Pension
plan
e.g. Benefits application program
19
Data Redundancy cont.

• Problems
• extra effort required to input the duplicate data
• additional computer storage needed to store the
  duplicate data
• possibility for data inconsistencies
• name recorded with different spellings or format
  (surname first or initials or forenames first)
• change of address recorded only by one of the
  dept.

20
Database Approach
DBMS
data files
21
Introduction to DBMS - OBJECTIVES cont.

• Explain the difference between conceptual,
  external and physical schemas and the reasons for
  a three-schema architecture for databases