2177. Migration validation: Find records that exist in source but not in target after a migration. — Node.js + Express + mysql2

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

In a migration validation module, solve this as a production problem using Node.js + Express + mysql2: Find records that exist in source but not in target after a migration. 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

DELETE FROM table_name;

Additional Explanation

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

Verified

Option B

UPDATE table_name SET status='active';

Additional Explanation

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

Verified

Option C

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 D

SELECT s.id FROM source_table s LEFT JOIN target_table t ON t.id=s.id WHERE t.id IS NULL;

Additional Explanation

This anti-join exposes missing target rows before source cleanup.