47. ON DELETE SET NULL

DBMS Published 30 Sept 2026 Updated 28 Oct 2026 3 Views Verified

Keep an employee row but clear manager_id when the manager is deleted.

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Answer & Explanation

4 Answers

Verified Correct Answer

Option A

ALTER TABLE employees ADD CONSTRAINT fk_employee_manager FOREIGN KEY (manager_id) REFERENCES employees(id) ON DELETE SET NULL;

Additional Explanation

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

Verified

Option B

ON DELETE UPDATE;

Additional Explanation

This option is incorrect for the stated requirement.

Verified

Option C

ON DELETE REMOVE;

Additional Explanation

This option is incorrect for the stated requirement.

Verified

Option D

ON DELETE CASCADE is identical to SET NULL.

Additional Explanation

This option is incorrect for the stated requirement.