The document presents an overview of the Entity-Relationship (E-R) Model, a logical representation of data used to describe the elements and relationships within an organization, introduced by Peter Chen in 1976. It details major components such as entities, attributes, and relationships, distinguishing between strong and weak entities, and discussing various types of attributes. Additionally, it highlights advantages like conceptual simplicity and effective communication for database design.

1. Presentation on Entity-Relationship
diagram

2. Entity Relationship Model
• Entity Relationship Model is a logical representation of
data in an organization. OR
• A semantic data model, used for the graphical
representation of the conceptual database design
• It is used to describe the elements of a system and their
relationship.
• It was introduced be peter Chen in 1976.

3. Entity Relationship Model
• Advantages of E-R Model
– Conceptual simplicity
– Visual representation
– Effective communication tool

4. Entity Relationship Model
 Major Components
 Entities
 Attributes
 Relationships

5. Entity Relationship Model
• Entities
– An entity is a person, place, thing or event for
which data is collected and maintained.
– For Example, a library system may contain
data about different entities like BOOK and
MEMBER.
– A college system may include entities like
STUDENT, TEACHER, COURSE and CLASS
etc.

6. Entity Relationship Model
• Some examples of entities are as follows.
– Person: TEACHER, PLAYER, DOCTOR
– Place: COUNTRY, CITY
– Object: VEHICLE, TOY, FURNITURE
– Event: PURCHASE, ADMISSION,
REGISTRATION
– Concept: ACCOUNT, PROGRAMMING
• The entity is used in three meanings that
are as follow

7. Entity Relationship Model
• Entity Type
– It is collection of entity having common
attribute.
– All entities in an entity type share common
characteristics. It is also Known as entity
class.
– For Example , STUDENT entity class is a set
of all students.

8. Entity Relationship Model
• Entity Instance
– An entity instance is a single occurrence of
an entity.
– For Example , a student Abdullah of
STUDENT entity type is an entity instance.

9. Entity Relationship Model
• Entity Set
– A set of all entities of a particular entity type
in the database at a given point of times is
called as entity set.
– For Example , an entity set student may
consist of all student in the university.

10. Types of Entities
• Types of Entities
– The following are the types of entities in
DBMS
• Strong Entity
– The strong entity has a primary key. Weak
entities are dependent on strong entity. Its
existence is not dependent on any other
entity.
– Strong Entity is represented by a single
rectangle −

11. Types of Entities
• Weak Entity
– The weak entity in DBMS do not have a
primary key and are dependent on the parent
entity. It mainly depends on other entities.
– Weak Entity is represented by double
rectangle −

12. Types of Entities
• Example of Strong and Weak Entity
– The example of strong and weak entity can be
understood by the below figure.
– The Strong Entity is Professor,
whereas Dependent is a Weak Entity.

13. Elements of E-R Model
• Attributes describe the characteristics or
properties of an entity in a database table.
An entity in a database table is defined
with the ‘fixed’ set of attributes.
• For example, if we have to define a
student entity then we can define it with
the set of attributes like roll number, name,
course.
• The attribute values, of each student
entity, will define its characteristics in the
table.

14. Entity-Relationship Diagram
• Attributes
– Entities has attributes, which can be
considered as properties describing it, for
example, for Teachers entity, the attributes
are Teacher_Name, Teacher_Address,
Teacher_Subject, etc. The attribute value
gets stored in the database.

15. Entity-Relationship Diagram
 Multivalued Attribute
 An attribute that has multiple values for a single entity at a time
is called a Multivalued Attribute.
 For example, technical skills of a student that can be
programming, web development, etc.

16. Entity-Relationship Diagram
 Composite Attribute
 If an attribute has two or more other attributes, then it is called
a Composite Attribute.
 For example, Student Name can be divided as Student First
Name, Student Middle Name, and Student Last Name.

17. Entity-Relationship Diagram
• Derived Attribute
– As the name suggests, the derived attribute is
an attribute whose value can be calculated
from another attribute.
– For example, Student Age can be derived
from Date-of-birth of a student.

18. Thank You