995. Auto set task completion time — trigger case 4

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

Implement the database trigger for this integrity/audit requirement. Consider NULL-safe comparisons and transaction behavior.

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Answer & Explanation

4 Answers

Verified

Option A

Use a SELECT-only query and do not enforce the rule.

Additional Explanation

This option is incorrect for the stated requirement.

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Option B

Use a trigger that recursively updates the same table without safeguards.

Additional Explanation

This option is incorrect for the stated requirement.

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Option C

Use a foreign key for an audit event that has no parent key.

Additional Explanation

This option is incorrect for the stated requirement.

Verified Correct Answer

Option D

DELIMITER // CREATE TRIGGER trg_task_complete BEFORE UPDATE ON tasks FOR EACH ROW BEGIN IF NEW.status='completed' AND OLD.status<>'completed' THEN SET NEW.completed_at=NOW(); END IF; END // DELIMITER ;

Additional Explanation

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