CS Professional · Artificial Intelligence, Data Analytics and Cyber Security - Laws and Practice · Database Management
While designing a database for a company's statutory registers, a designer represents 'Director' as a rectangle and 'Director ID' as an oval attached to it in an Entity-Relationship diagram. In this notation, what does the oval represent?
The oval represents an attribute of the entity. In ER notation, entities are rectangles, relationships are diamonds and attributes are ovals, so Director ID is a property describing the Director entity rather than a relationship, weak entity or cardinality constraint.
- AAn attribute describing the entityCorrect
- BA relationship between two entities
- CA weak entity dependent on another entity
- DA cardinality constraint between entities
Explanation
In an ER diagram, rectangles denote entity sets, diamonds denote relationships and ovals denote attributes. Director ID is a property of the Director entity, so the oval is an attribute. It is not a relationship, which would be drawn as a diamond.
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