Database Management System × Entity-Relationship Model

Relationships and Relationship Types

Posted by AJ × 03:27

A relationship relates two or more distinct entities with a specific meaning. For example, EMPLOYEE John Smith works on the ProductX PROJECT, or EMPLOYEE Franklin Wong manages theResearch DEPARTMENT.

Relationships of the same type are grouped or typed into a relationship type. For example, the WORKS_ON relationship type in which EMPLOYEEs and PROJECTs participate, or the MANAGES relationship type in which EMPLOYEEs and DEPARTMENTs participate.

The degree of a relationship type is the number of participating entity type. Both MANAGES and WORKS_ON are binary relationships.