Question

What do you understand by relationship type? How is it different from relationship instance and relationship set?

Answer 1

The relationship between various entities that belong to different entity types in a specific manner is known as a relationship type.

A collection of various relationships that belongs to the same relationship type is called a relationship set. The result that is derived from the relationship type is known as instance and is shown in an entity set. The relationship prepared between the two entity types: Salary Slips and Employees, associates each salary slip with the employee who prepared it. Similarly, another example of relationship type of STUDY_IN associates one student entity and one class entity. In this example, Student and Class are entities and the relationship between i.e. STUDY_IN is the relationship set.

In the following ER diagram, the relationship types are shown in a diamond-shaped box. The participating entities are shown in the rectangular boxes, which are connected to the diamond-shaped box through straight lines.