Relationship Types

Relationship Types

* A relationship is an association among two or more entities.diamond

* A collection of similar relationships is called a relationship set.

* For example, ‘Branch’ and ‘Staff’ can be associated with a relationship ‘Has’.

* Relationship occurrence – a uniquely identifiable association, which includes one occurrence from each participating entity type.

Relationship type – diagrammatic representation

Shown as a line connecting the associated entity types, labelled with the name of the relationship.

First letter of each word in the entity name is uppercase.
Normally a relationship is named using a ‘verb’ or ‘verb group’.
The direction in which the relationship makes sense is marked using an ‘arrow’.

Degree of Relationship type

The number of participating entity types in a relationship.

Relationships can be classified based on their degree into

Binary – relationship with two participants
Ternary – relationship with three participants
Quaternary – relationship with four participants

Degree of a relationship is the number of participating entities in the relationship.

A relationship of degree two is called a binary relationship (e.g. Works In).

A relationship with degree three is called ternary.