This Ppt only about Relational Model and it's utility in Database management System

1. RELATIONAL MODEL AND ITS
UTILITY
REPRESENTOR:-
NAME-RAJKUMAR MONDAL
COURSE-BSC(IT)
E.NO-A35404916005

2. RELATIONAL DATA MODEL
The relational data model uses a collection of
tables to represent both data and relationship.
This Concept was purposed by Dr. E.F. Codd,
A researcher of IBM in the year 1960.

3. The Relation datamodel has following properties:
Each table may have multiple columns.
Each columns have unique values.
Relational model comes under the record based data model.
Fixed format attributes exists.

4. Relation
The column headers of a table are called attributes and for each attribute ai there is a set of
permitted values called the D of a
Given the domains D1, D2,..., D ,a relation r is defined as a subset of the cartesian product
D1*D2*...*D
degree
attribute
a1 a2 a
name street …. city
Rohan Housing
colony
…. Dhanbad
…. …. …. ….
cardinality
Relation r
tuples
D1 D2 D
n
n
n
n
ii

5. Keys of a Relation
It is a set of one or more columns whose combined whose value
are unique among all occurrences in a given table.A key is the
relational means of specifying uniqueness.
Some different types of keys are:
1.PRIMARY KEY
2.SUPER KEY
3.CANDIDATE KEY
4.FOREIGN KEY

6. Primary key:- A key that we choose to identify rows uniquely is called a
Primary key.
Candidate Key:- Superkey for which no proper subset is a superkey,then
such minimum Superkey is called Candidate key.
Example:- Teacher
Tno# Tname Sub
T01 A Comp.Sc
T02 B English
T03 C Phy
T04 D Chem.
T05 E Comp.Sc
Primary key
Candidate key
Primary key and Candidate key

7. Super Key:- A set of single attributes or a group of attributes which
uniquely identified each entity in the entity set
Foreign Key:- If two table can be related using a common attribute
then the primary key of one table is also available as an
attribute in another related table,then it is called
Foreign Key
Customer id
Name
Street
Pincode
city
Order Id
Customer Id
Cd Id
Date
Amount
status
Cd Id
name
Duration
Price
year
customer order Cd
Schema Diagram

8. OPERATION IN RELATIONAL MODEL
There are four basic operations:-
1.Insert
2.Update
3.Delete
4.Retrieve

9. Advantages of Relational Model
The major advantages of the relational model are:-
1.This model is easy to use.It is very natural and attractive model.
2.This model is flexible.It is very easy to link two or more tables.
3.Sequrity control and authorization can also be implemented more
easily.
4.Data independence is achieved more easily with normalization.

10. Disadvantages of Relational Model
Some of the disadvantages are:-
1.Machine Performance
2.Hardware Overheads
3.Ease of design can lead to bad design