Reviewed by Aditya Kumar · Last reviewed 2026-03-24
Example combining joins, aggregations, windows: WITH base AS (SELECT r.region, p.product, SUM(s.amount) amt FROM sales s JOIN regions r ON s.region_id = r.id JOIN products p ON s.product_id = p.id GROUP BY r.region, p.product), ranked AS (SELECT *, ROW_NUMBER() OVER (PARTITION...
Example combining joins, aggregations, windows: WITH base AS (SELECT r.region, p.product, SUM(s.amount) amt FROM sales s JOIN regions r ON s.region_id = r.id JOIN products p ON s.product_id = p.id GROUP BY r.region, p.product), ranked AS (SELECT , ROW_NUMBER() OVER (PARTITION BY region ORDER BY amt DESC) rn FROM base) SELECT FROM ranked WHERE rn <= 5. Why: JOINs for dimensions; GROUP BY for aggregates; window for ranking. Adjust to required output. Architecture: Structure with CTEs for readability and optimizer.
Red Flag: Monolithic query without CTEs. Pro-Move: 'CTEs for each logical step; EXPLAIN to validate plan.'
According to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains an editor-reviewed database of 1,863 data engineering interview questions across 7 categories.