Relationship Instance and the Degree of a Relationship Type

For Complete YouTube Video: Click Here

In this class, we will understand Relationship Instance and the Degree of a Relationship Type.

We have already discussed the concept of Identifying the relationship types.

Table of Contents

A relationship instance in R is an association of entities, where the association includes exactly one entity from each participating entity type.

We will consider the relationship type works for and try to understand relationship instances.

The image below shows the relationship instances of the entities of the entity types participating in the relationship.

In the above image, the relationship instance r1 is associating the entity e1 with the department d1.

This association states that employee e1 works for department d1.

Similarly, the relationship instance r2 is associating the employee e2 and the department d2.

That means employee e2 works for department d2.

The degree of a Relationship Type is the number of participating entity types.

In the above image, the degree of a relationship type R is binary because two entity types are participating in the relationship type.