Reviewed by Aditya Kumar · Last reviewed 2026-03-24
**Architectural Logic**: Two approaches. 1. GROUP BY + ORDER BY + LIMIT: SELECT customer_id, SUM(sales_amount) total_sales FROM sales GROUP BY customer_id ORDER BY total_sales DESC LIMIT 5. 2. Window: SELECT * FROM (SELECT customer_id, SUM(sales_amount) total_sales, RANK() OVER...
This medium-level SQL question appears frequently in data engineering interviews at companies like Daniel Wellington, Goldman Sachs, Swiggy. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (partition, window) will help you answer variations of this question confidently.
Break this problem into components. Identify the core trade-offs involved, then walk the interviewer through your reasoning step by step. Demonstrate awareness of edge cases and production considerations - this is what separates good answers from great ones.
Architectural Logic: Two approaches. 1. GROUP BY + ORDER BY + LIMIT: SELECT customer_id, SUM(sales_amount) total_sales FROM sales GROUP BY customer_id ORDER BY total_sales DESC LIMIT 5. 2. Window: SELECT * FROM (SELECT customer_id, SUM(sales_amount) total_sales, RANK() OVER (ORDER BY SUM(sales_amount) DESC) rk FROM sales GROUP BY customer_id) t WHERE rk <= 5. Why: LIMIT is simpler, stops early in some engines. RANK handles ties (multiple customers with same total); DENSE_RANK if ties should share rank. Scalability: Both require full aggregation; no early termination. Partition pruning on sales (e.g., by date) reduces input. Cost: Window adds sort overhead; for strict top 5, LIMIT is cheaper.
Red Flag: Using LIMIT 5 when business expects 'top 5 including ties'—inconsistent. Pro-Move: 'I confirm with product: strict 5 or include ties? RANK for leaderboard semantics.'
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According to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 3 companies. DataEngPrep.tech maintains an editor-reviewed database of 1,863 data engineering interview questions across 7 categories.