Roles in E-R Diagrams in DBMS

Roles in E-R Diagrams

• ·         It is a function that plays(relationship) in an entity called its role.
• ·         Roles are normally explicit and not specified.
• ·         Useful when the relationship meaning needs to clarify.
• ·         Example, The relationship works-for define in employees as manager or worker. The labels “manager” and “worker” are called roles; they specify how employee entities interact via the works-for relationship set.
• ·         Roles are indicated in E-R diagrams by labeling the lines that connect diamonds to rectangles.
• ·         Role labels are optional and are used to clarify the semantics of the relationship.

 

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