CBSE Compartment 2025, Set 4

Question

**Assertion (A):** There can be multiple primary keys in a relation. 
 
**Reason (R):** There can be multiple candidate keys in a relation but only one of these is chosen as primary key. A). Both Assertion (A) are true and Reason (R) is the correct explanation for Assertion (A). B). Both Assertion (A) are true and Reason (R) is not the correct explanation for Assertion (A). C). Assertion (A) is true, but Reason (R) is false. D). Assertion (A) is false, but Reason (R) is true.

Edvaya · Accepted Answer

The correct answer is Assertion (A) is false, but Reason (R) is true.. **Assertion (A) is False:** By definition, a relation (table) can have one and strictly only one Primary Key constraint (although it may consist of multiple columns acting as a composite key). **Reason (R) is True:** A table can possess several attributes that uniquely identify a record (Candidate Keys), but the database designer selects only one of them to act as the official Primary Key.

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Informatics Practices > Database Query Using Sql > Querying And Grouping

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