Question

Assertion (A): The PRIMARY KEY constraint in SQL ensures that each value in the column(s) is unique and cannot be NULL.

Reason (R): Candidate keys are not eligible to become a primary key.

Options

• Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation for Assertion (A).

• Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation for Assertion (A).

• Assertion (A) is true, but Reason (R) is false.

• Assertion (A) is false, but Reason (R) is true.

Answer 1

Assertion (A) is true, but Reason (R) is false.

Explanation:

1. Assertion (A) is True: A PRIMARY KEY uniquely identifies each record in a table. By definition, it must contain unique values and cannot contain NULL values.
2. Reason (R) is False: This statement is incorrect because Candidate Keys are specifically the columns that are eligible to become a primary key. In fact, the Primary Key is simply a candidate key that has been chosen by the database designer.