2305. Messaging: Fetch the latest message in each conversation. — Python + FastAPI + SQLAlchemy

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

In a messaging module, solve this as a production problem using Python + FastAPI + SQLAlchemy: Fetch the latest message in each conversation. Provide the SQL, explain the logic, show safe application integration, and mention failure/edge cases.

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Answer & Explanation

4 Answers

Verified Correct Answer

Option A

SELECT * FROM (SELECT m.*,ROW_NUMBER() OVER(PARTITION BY conversation_id ORDER BY created_at DESC,id DESC) rn FROM messages m) x WHERE rn=1;

Additional Explanation

Partition by conversation and rank newest first.

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

DELETE FROM table_name;

Additional Explanation

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

Verified

Option D

SELECT * FROM table_name;

Additional Explanation

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