**ROW_NUMBER()** assigns unique sequential numbers (1,2,3...) even for ties. **RANK()** gives same rank for ties, gaps after (1,2,2,4). **DENSE_RANK()** same rank, no gaps (1,2,2,3). **Use ROW_NUMBER when**: Need exactly N rows per group (e.g., top 1 per user)—deterministic with...
This medium-level SQL question appears frequently in data engineering interviews at companies like Bitwise. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (partition) 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.
ROW_NUMBER() assigns unique sequential numbers (1,2,3...) even for ties. RANK() gives same rank for ties, gaps after (1,2,2,4). DENSE_RANK() same rank, no gaps (1,2,2,3). Use ROW_NUMBER when: Need exactly N rows per group (e.g., top 1 per user)—deterministic with ORDER BY. Use RANK/DENSE_RANK when: Ties should share rank (e.g., leaderboards). Pro of ROW_NUMBER: Deterministic; predictable row count. Con: Arbitrary tie-break. Pro of DENSE_RANK: Handles ties meaningfully. Con: Can return more than N rows for "top N". Scalability: All are O(n) per partition; choose based on business rule.
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Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.