3938. Customers: Find the top customer by completed revenue in each city. — Architecture

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

In a customers module, solve this as a production problem using Architecture: Find the top customer by completed revenue in each city. 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

SELECT * FROM table_name;

Additional Explanation

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

Verified

Option B

DELETE FROM table_name;

Additional Explanation

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

Verified

Option C

UPDATE table_name SET status='active';

Additional Explanation

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

Verified Correct Answer

Option D

WITH totals AS (SELECT c.city,c.id,c.name,SUM(o.total_amount) revenue FROM customers c JOIN orders o ON o.customer_id=c.id AND o.status='completed' GROUP BY c.city,c.id,c.name) SELECT * FROM (SELECT totals.*,ROW_NUMBER() OVER(PARTITION BY city ORDER BY revenue DESC,id) rn FROM totals) x WHERE rn=1;

Additional Explanation

Aggregate revenue first, then rank within each city.