32. NULL

DBMS Published 30 Sept 2026 Updated 30 Sept 2026 0 Views Verified

Why is NULL not normally compared with = in SQL?

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Answer & Explanation

4 Answers

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Option A

NULL always equals zero.

Additional Explanation

This option is incorrect for the stated requirement.

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Option B

NULL always equals an empty string.

Additional Explanation

This option is incorrect for the stated requirement.

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Option C

NULL is automatically converted to false in every expression.

Additional Explanation

This option is incorrect for the stated requirement.

Verified Correct Answer

Option D

NULL represents an unknown or missing value, so SQL uses three-valued logic; IS NULL and IS NOT NULL are used for null checks.

Additional Explanation

Correct implementation. Prefer parameterized queries in application code, validate affected rows for UPDATE/DELETE, and use transactions for related writes.