- An Entity-Relationship
Model is generated through ER Diagram i.e. known as Entity
Relationship Diagram which constitutes various symbols with the help of
which entities, attributes, and relationships are represented
- Each of these components has a separate
notation. Let’s discuss them together and later you can have your knowledge
check through this
1. Entity: The entity is an ER Diagram is
denoted through a rectangle. These rectangles are named according to the names
For example: Let the entities be Company, Course, Class, and
Loan. Then they will be represented as :
Entity: When attributes of an entity are not capable of determining
the entity uniquely, it is called a weak entity. The weak entity in an ER
Diagram is denoted through a double rectangle.
For example: In
a bank, the bank branch can be deduced as a weak entity as its attributes
are not enough to determine it uniquely.
Relationship: The relationship in an Entity Relationship Diagram is
denoted through a diamond.
For example: A
person works in a company can be described using a relationship as
Attributes: An Attributes in an ER Diagram are denoted through an
example: A university acting as an entity can have multiple
attributes like name, location, courses, colleges, etc.
Attribute: The key attribute is a type of attribute which alone can
determine the entity uniquely. These are denoted through an ellipse with an
example: A bank customer can be uniquely identified through
his/her account number.
Attribute: Multi-valued attributes in an Entity Relationship Diagram
are denoted through the double ellipse.
example: An account holding customers of the bank can have
multiple emails, multiple mobile numbers, and even multiple
addresses(Permanent and Corresponding). They can be termed as multi-valued
Multi-Valued Attribute Example
Attributes: A Composite attributes in an Entity Relationship Diagram
are denoted by the linked ellipse.
For example: Let the name of a person(First Name + Middle Name +
Composite Attribute Example
Attribute: The Derived attributes in an ER Diagram(Entity
Relationship Diagram) are represented using dashed ellipse.
For example: Think of a class having some students. Each of them
can have their name, address, and age. We can derive the average age of the
student from already present data in the database.
Participation of Entity in Relation: In this type, every entity is
fully involved and linked in the relationship and this participation is denoted
using double lines.
Participation of Entity in Relation: As the name suggests, some of
the entities participate in the relationship fully and some of them participate
partially. Partial relation in ER Diagram is denoted using a single