This document provides an introduction to database systems. It defines key concepts like data, information, metadata and databases. It explains that a database management system (DBMS) is software that creates and manages large databases efficiently. The document discusses limitations of traditional file processing systems and how databases address these issues through centralized data storage, standardized access, and enforcing data integrity rules. It also describes the three levels of data abstraction in databases - physical, conceptual and external schemas.

1. DATABASES
CHAPTER 1
INTRODUCTION TO
DATABASE SYSTEMS

2. 2
Where do we begin?
 What is ‘data’?
 Data
 raw facts
 text, graphics, images, sound and video
segments that have meaning in the users’
environment.
 Information
 data processed to increase knowledge in the
person using the data

3. 3
 What is Metadata ?
 “data about data”
 i.e. data describing the properties or
characteristics of data.

4. 4
What is a database?
 Database
 An organized collection of logically related data
 Users of a database can do:
 Add new files to the database.
 Remove (Delete) files from the database.
 Insert data into existing files.
 Retrieve data from existing files.
 Change/Delete data in existing files.

5. 5
What is a DBMS?
 DBMS (Database Management System)
 A software for creating and managing large
databases efficiently.
 E.g.
 Oracle
 MSAccess
 Sybase
 MySQL

6. 6
Need for a DBMS
 To be able to appreciate why we need a DBMS, we must look at what are
the limitations of the file processing system (FPS) traditionally used for
accessing huge amount of data.
 So, what is a FPS?
 One of the ways to store, manipulate and retrieve large files of data.
 For example : a savings bank.
 Two types of files
 Account File
 Customer File.
 A separate computer program is written to accomplish the
following tasks
 Debit or Credit an Account
 Add a new account.
 Find an account balance.
 Generate monthly statements.
 Each program defines and manages its own data.
 Development of the system proceeds as follows:
 New application programs must be written as the need arises.
 New permanent files are created as required.

7. 7
File Processing System

8. 8
1. Program-data dependence
Since in a TFPS, each application program accesses the
data files directly, programs are dependent on how data is
structured and stored giving rise to the following problems.
 Each application program needs to include code for the
metadata of each file
 Each application program must have its own processing
routines for reading, inserting, updating and deleting
data
 Lack of coordination and central control
 Non-standard file formats
 Changes in data structuring requires changing all the
application programs that reference it.
So, what are the problems with the
straight file-processing approach?

9. 9
2. Difficulty in accessing data
 May have to write a new application program to
satisfy an unusual request.
 E.g. find all customers with the same postal
code.
 Could generate this data manually, but a long
job...
3. Data redundancy and inconsistency
 Since in FPS, new files are created as
required, same information may be duplicated in
several places leading to data redundancy.
 All copies may not be updated properly resulting
in inconsistent data.

10. 10
4. Multiple Users
 Want concurrency for faster response time.
 Need protection for concurrent updates.
 E.g. two customers withdrawing funds from the
same account at the same time - account has
$500 in it, and they withdraw $100 and $50.
The result could be $350, $400 or $450 if no
protection.
5. Security problems
 Every user of the system should be able to
access only the data they are permitted to see.
 E.g. payroll people only handle employee
records, and cannot see customer accounts;
tellers only access account data and cannot
see payroll data.
 Difficult to enforce this with application
programs.

11. 11
6. Integrity problems
 Data may be required to satisfy constraints.
 E.g. no account balance below $25.00.
 Again, difficult to enforce or to change
constraints with the file-processing approach.
 These problems and others led to the development
of database management systems.

12. 12
SOLUTION: The DATABASE
Approach
 Central repository of shared data
 Data is managed by a controlling agent (a
Database Management System (DBMS).
 Stored in a standardized, convenient form

13. 13
DBMS manages data
resources like an operating
system manages hardware
resources
DBMS Database
containing
centralized
shared data
Application
#1
Application
#2
Application
#3
Database Management System

14. 14
Functions of DBMS
 Data Abstraction
 The major purpose of a database system is to
provide users with an abstract view of the
system.
 The system hides the details of how data is stored
and created and maintained.
 There are three levels of abstraction:
 Physical Level:
 Conceptual Level:
 View Level:

15. 15
External schema
Different people have
different views of the
database…these are the
external schema
Internal schema
Three-schema database architecture

16. 16
Three levels of data abstraction
 Physical Schema:
 Is concerned with how the data is stored in the computer’s hard-disk.
 Lowest level of abstraction.
 Complex low-level structures described in detail.
 Conceptual Schema:
 Next highest level of abstraction.
 a detailed specification of the overall structural organization of the
data.
 Specifically, what data is stored in the database and the relationships
among the data (ER Models).
 Database administrator level.
 External Schema or User-View Schema:
 Highest level.
 Describes part of the database for a particular group of users.
 Can be many different views of a database.
 E.g. tellers in a bank get a view of customer accounts, but not of
payroll data.

17. 17
Advantages of Database
Approach
1. Program-Data Independence
 Metadata is stored in DBMS, so applications don’t
need to worry about data formats.
 Data queries/updates are managed by DBMS so
programs don’t need to process data access
routines
 Allows the physical and (or) conceptual database
schema to be altered without having to rewrite the
application programs.

18. 18
Advantages of Database
Approach
2. Minimal Data Redundancy
 Leads to increased data integrity/consistency
3. Improved Data Sharing
 Different users get different views of the data
4. Enforcement of Standards
 All data access is done in the same way

19. 19
Advantages of Database
Approach
5. Improved Data Quality
 Constraints, data validation rules
6. Better Data Accessibility/ Responsiveness
 Use of standard data query language (SQL)
7. Security, Backup/Recovery, Concurrency
 Disaster recovery is easier

20. 20
The Database Approach
 Database Application (DA)
 application program used to perform a series of
database operations or activities on behalf of database
user.
E.g create, read, update, delete

21. 21
Types of Database Application
 Personal Computer Database
 support one user (standalone desktop database)
 Workgroup Database
 small team of people work together on the same project
or application (LAN <25 users)
 Department Database
 functional unit within an organization (LAN 25-100 users)
 Enterprise Database
 support organization-wide operation and decision
making (WAN hundreds/ thousands of users)

22. 22
Component of Database Environment
 CASE (Computer Aided Software Engineering Tools)
 tools used to design databases and application programs.
 Categories:
 Upper-CASE
 Lower-CASE
 Integrated-CASE
 Repository
 centralized knowledge base of all data definitions, screen, data relationships, report
formats and other system components.
 DBMS
 Database – storehouse of the data
 Application programs
 User Interface
 Data Administrators – personnel responsible for maintaining the database
 System developers – personnel responsible for designing databases and software
 End users

23. 23
Components Of The Database Environment

24. 24
“Users” of a Database
 End Users
 use application programs, queries or reports
prepared by developers (e.g. users of ATM)
 Application programmers / developers
 are computer professionals who write the
application programs, reports, queries, etc.
 Database administrator
 handle security & authorization, recovery from
crashes, tuning for performance, etc

25. END..

26. Exercise
 Find ONE example of database system for
each of the following.
 Personal Computer Database
 Workgroup Database
 Department Database
 Enterprise Database
 Capture the interface and briefly describe for
each.
26