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