47. ON DELETE SET NULL

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

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

Looking for the latest Sarkari Result 2026 updates? Check the latest government exam results, merit lists and result updates on Sarkari Resultess.

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.