1. E-R
Diagram

2. Presented by:
Fatiha Rashid
Javeria
Rafeeq

3. Logical representation of data in an
organization.
Views the entire system as a collection
of entities related to one another.
Introduced by peter chen in 1976.

4. Advantages of E-R Model:

5. Elements of E-R
Model:
1: Entities
2: Attributes
3: Relationships

6. Entities:
An Entity is a Person,Place,Thing or
Event for which data is collected and
maintained.
•Represented by a rectangle
Entity namesymbol

7. Entitytype/Entityclass:
A set of entities with same attributes
Exmaple: Student entity class is a set of All
students.
Book entity type is for all Books etc.

8. Entity instance
A member of an entity class is known
as entity instance .
Also known as entity occurrence.

9. Entity Class
Entity
instance

10. Entity class
Entity instance

11. Example:
Name, address,Class
and Email of a students
are his attributes. Attribute name
Symbol

12. Attribute Domain:
*A set of possible values for an
attribute
*All atributes have domain
Example : The domain for Grade
point average (GPA) can be from 0
to 4.

13. *A logical connection between different enities.
* Established on the basis of interaction between these
entities.
Participents: entities participating In a relationship are
called participents.
Relationship
name

14. Doctor treats Patient
Teacher teaches students

15. If all entities of that entity set may be participant in
the relationship.
Example: In supplier_part relationship,the
relationship is total if every part is supplied by a
supplier.
If some of the entities of that entity set may be
participant in the relationship.
Example: If certain parts are available without a
supplier.

17. 1: Simple
2: composite
3: single valued
4: multi-valued
5: stored
6: derived
7: identifiers

18. *Cannot be subdivided into smaller
components.
PERSON
GENDER

19. *Can be divided into smaller components.
EMPLOYEE
ADDRESS
street
city
country

20. Single-valued Attributes:
Contain single valued value.
Employee
Gender
Multi-valued Attributes:
Contain two or more values.
person
name
city hobies

21. *Stored in a database.
*Not stored in database but derived
from another value.

22. Identifies an entity
instance among other
instances In entity class.

24. week entity Can exist only if any other entity
exist, also called child ,dependent .
Strong entity Can exist without depending upon the
existance of another entity .
PERSON HAS CHILDCHILD
Owner/ identifying
owner:
entity on which the
weak entity depends.Example

25. Type of entity that associates the
instances of one or many entity type
with one another.

26. •The number of entities in a relationship .
•Types:
•1: unary relationship
•2: binary relationship
•3: ternary relationship

28. Exist between the instances of two
entity types.
Types:
1: one-to-one
2:one-to-many
3:many –to-many

31. The maximum number of
relationships.

32. *Circle means zero
*Line means………..one
*Crow’s foot symbol
means….many

34. employee
department
jobs
equipment
suppliers project

35. name DOB
Phone no
Project
no
Project
name
Project
cost duration
name Address
Date of last meeting
number