3111. Trigger: Prevent negative account balance on direct debit updates. — Production Debugging

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

In a trigger module, solve this as a production problem using Production Debugging: Prevent negative account balance on direct debit updates. Provide the SQL, explain the logic, show safe application integration, and mention failure/edge cases.

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Answer & Explanation

4 Answers

Verified

Option A

UPDATE table_name SET status='active';

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.

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Option B

SELECT * FROM table_name;

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.

Verified Correct Answer

Option C

DELIMITER // CREATE TRIGGER trg_debit BEFORE UPDATE ON accounts FOR EACH ROW BEGIN IF NEW.balance<0 THEN SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT='Insufficient balance'; END IF; END // DELIMITER ;

Additional Explanation

A database constraint/trigger can provide defense-in-depth, though transaction design should still enforce business rules.

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Option D

DELETE FROM table_name;

Additional Explanation

Incorrect: it does not satisfy the stated business rule and can return/change unintended data.