Chapter 4, Problem 13RQ

Explanation of Solution

Composite entity:

A composite entity is normally used to convert M: N relationships into 1: M relationships. It is also referred as “bridge entity”, which has a primary key (PK) composed of multiple attributes.

• The PK attributes are inherited from the entities, which it associates to one another.

Usage of composite entity in ERD:

In the Entity Relationship Management (ERM), an M: N relationship is effective at the conceptual level. But when implementing the ERM in a relational database, the M: N should be mapped to a set of 1: M relationships using “composite entity”.

Example:

Consider the entities CLASS and STUDENT with M: N relationship defined by following business rules:

• A student can take several classes...