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Computer Science · 2026 · 1 mark
CBSE 2026 · Central · Set 4 · Q21
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…
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.
Official answer
(C)
Assertion (A) is true, but Reason (R) is false.
Marking-scheme solution
(C)
Assertion (A) is true, but Reason (R) is false.
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CBSE Class 12 Computer Science past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.