Entity Relationship Model

1. DATA
MODELS
Entity Relationship
Model
DBMS
In Hindi

2. Data Models
• A Model is a representation of reality, ‘real world’ objects and events,
associations.
• Data Model is a collection of high level concepts that can be used to
describe the structure of a database that hide many low levels storage
details.
• Data Model can be defined as an integrated collection of concepts for
describing and manipulating data, relationship between data, and
constraints on the data in an organization.

3. The Entity Relationship Model (ER Model)
• Entity–Relationship modeling was developed for database and design by
Peter Chen in 1976
• Entities are things or an object in the real world that is distinguishable
from other objects based on the values of the attributes is posses.
• Entities are described in a database by a set of attributes. For E.g.
Student is an entity which has attributes like RollNo, Name, DateOfBirth.
• An entity set is a collection of same type of entities that share same
attributes.
• Relationship is an association among several entity set. For E.g Student
is “admitted” to a single branch (Computer , Electronics etc.)

4. Entity, Entity-Set and Attributes
Student Table
Roll_No Name Date_Of_Birth
1 Ajay Joshi 12/3/2000
2 Poonam Sharma 28/4/2000
3 Vinay Deshmukh 29/12/1999
Attributes
Entity Set
Entity

5. ER Diagram
• ER Model is represented by using ER Diagram.
• Entity Set is represented by “Rectangle”
• Relationship is represented by “Diamond”
• Attributes are represented by “Ellipses”
• Linking of attributes to entity sets and entity sets to relationships is by “Lines”
Branch Student
Admitted
DateOfBirth
Name
RollNo
Id BName

6. Types Of Entity Set
 Strong Entity Set : An entity set that contains sufficient attributes to
uniquely identify all its entities.
 Weak Entity Set: An entity set which does not have sufficient
attributes to uniquely identify all its entities.
Account Logs Transaction

7. Types Of Attributes
There are many types of attributes which are as follows:
Key attribute
Composite attribute Derived attribute
Single-value
attribute
Multi-value
attribute
Simple attribute

8. Key Attribute
This attribute has the unique value for an entity which is used to identified
given row in the table is called as key attribute of an entity. It is
represented by underlying the attribute name.
Student
Roll_No

9. Simple Attribute
Simple attributes are atomic values, which cannot be divided further. For
example, a student’s phone number is an atomic value of 10 digits. It is
simply represented by an oval.
Student
Roll_No PhoneNo

10. Composite Attribute
Composite attributes are made up of more than one simple attributes. For
example , a student complete name may have F_Name, M_Name and
L_Name.
Student
RollNo PhoneNo
Student_Nm
F_Name
M_Name
L_Name

11. Derived Attribute
Derived attributes are the attributes that do not exist in the physical database, but
their values are derived from other attributes present in the database. For
example age can be derived from DateOfBirth. It is represented by dashed oval.
Student
RollNo PhoneNo
DateOfBirth
Student_Nm
F_Name
M_Name
L_Name
Age

12. Single-value and Multi-value Attribute
• Single-value attributes contain single value. For example Aadhar_card-number
• Multi-value attribute may contain more than one values. For example a person
can have more than one phone number, email_address etc. It is represented by
double oval.
Student
RollNo PhoneNo
DateOfBirth
Student_Nm
F_Name
M_Name
L_Name
Age

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