Class - 12 CBSE Computer Science — Assertion Reason Type Questions
Assertion. The treatment of NULL values is different with PRIMARY KEY and UNIQUE constraints.
Reason. The column(s) with PRIMARY KEY do not allow the NULL value even in a single row but UNIQUE constraint allows NULL for one of the rows.
Answer
(a)
Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
Explanation
The treatment of NULL values is different with PRIMARY KEY and UNIQUE constraints. The UNIQUE constraint allows NULL values for one of the rows, while the PRIMARY KEY does not allow the NULL value in any row.