DATABASE MANAGEMENT SYSTEM

Prepared by

NIJAZ N

ORGANIZING DATA IN A TRADITIONAL FILE ENVIRONMENT

Organize data in fields ,records and files.

Field - A grouping of characters into a word, a group of words or a

complete number (eg: person’s name or age) is called a field.

Record – A group of related fields comprises a record (eg: student’s

name, course taken, date and grade)

File - A group of records of the same type (eg: course file)

Difficult to keep track of all the pieces of data.

Different functional areas and groups were allowed to develop their own

files independently.

PROBLEMS WITH FILE SYSTEM

Data Redundancy • Presence of duplicate data in multiple files so that

the same data are stored in more than one place or

location.

Data Inconsistency • Same data may have different values.

Lack of flexibility • Difficult to deliver ad hoc reports or respond to

unanticipated information requirements in a timely

fashions.

Poor Security •Little control over data or access of data.

Lack of Data Sharing • Information cannot flow freely across different

functional areas

DATABASE Is a collection of data organized.

Serve many applications efficiently by

Centralizing the data

Controlling the redundant data.

A single database services multiple application rather than storing data in

separate files for each application.

E.g.:-

A University database through which university applications from the

Registrar’s office, the Accounting department, and the Examination

department access data

DBMS

Software that defines a database, stores the data, supports a query

language, produces reports, and creates data-entry screens.

A DBMS is software that:

Acts as an interface between application programs and the data files.

Helps to reduce data redundancy and eliminate data inconsistency by

allowing a central, shared data source

Physical view

DBMS

Logical View

LOGICAL & PHYSICAL VIEW

Data as perceived by end users/business specialists

How data are actually organized on physical storage media

DBMSData

definition Language

DDL

DataDictionar

y

Data Manipula

tionLanguage

DML

DBMS – COMPONENTS/REQUIREMENTSFormal language used

by the programmers to specify the

structure/content of the database

Contains commands that permit end users to extract data from

the database to satisfy information requests

Automated/manual file that stores

definitions of data elements and data

characteristics

DATABASE MODELS /TYPES

Database Models

Relationship Model

Hierarchical Model

NetworkObject

Oriented

RELATIONSHIP MODEL

Proposed in 1969 by Edgar F. Codd

Depicts data logically as many-to-many relationships

All data is represented in terms of tuples, grouped into relations

Order list of elements

HIERARCHICAL MODEL

Organizes data in a tree-like structure

Supports one-to-many /parent-child relationships

Prevalent in large legacy systems

NETWORK MODEL

Depicts data logically as many-to-many relationships

Object types are nodes and relationship types are arcs

OBJECT ORIENTED MODEL

Organizes data in a tree-like structure

Supports one-to-many parent-child relationships

Prevalent in large legacy systems