1138. Batch processing — Library — implementation variant 38

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

In a Library application, implement this production problem: Select pending tasks for a worker without repeatedly processing the same rows. The API/service receives user input and must return or modify data safely. Give the SQL solution, explain why it works, and show how the same operation is called from the selected stack.

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Answer & Explanation

4 Answers

Verified Correct Answer

Option A

START TRANSACTION; SELECT id FROM tasks WHERE status='pending' ORDER BY id LIMIT 100 FOR UPDATE SKIP LOCKED; -- process; COMMIT;

Additional Explanation

Row locking plus SKIP LOCKED can support concurrent workers on compatible transactional engines.

Verified

Option B

SELECT * FROM the_table;

Additional Explanation

Incorrect: it does not implement the stated business rule and may modify/fetch the wrong rows.

Verified

Option C

DELETE FROM the_table;

Additional Explanation

Incorrect: it does not implement the stated business rule and may modify/fetch the wrong rows.

Verified

Option D

UPDATE the_table SET status='active';

Additional Explanation

Incorrect: it does not implement the stated business rule and may modify/fetch the wrong rows.