For which of the following is a separate relation schema created containing…
2024
For which of the following is a separate relation schema created containing that attribute together with the primary key of the entity set that owns it?
Answer: B. A multivalued attribute of an entity set — ConceptWhen an ER model is converted to relations, each construct is mapped according to its cardinality and key structure. A multivalued attribute cannot…
- A.
A many-to-many relationship set
- B.
A multivalued attribute of an entity set
- C.
A one-to-many relationship set
- D.
All of the mentioned
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Correct answer: B
Concept
When an ER model is converted to relations, each construct is mapped according to its cardinality and key structure. A multivalued attribute cannot occupy one atomic field in the owning entity relation, so its repeated values must be represented as separate tuples linked to that entity.
Application
For a multivalued attribute M of entity set E, create a relation containing M and the primary key of E; together they identify the repeated values belonging to each entity. This is exactly the schema composition stated in the question.
Contrast
A many-to-many relationship is also mapped to a separate relation, but that relation contains the primary keys of both participating entity sets, plus any relationship attributes.
A one-to-many relationship is normally represented by placing the primary key of the one side as a foreign key in the relation on the many side.
Because these constructs use different mappings, the universal choice does not describe a single shared schema form.
Result
The described relation schema is the mapping for a multivalued attribute of an entity set.