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Home/Questions/SQL/Why not use ROW_NUMBER() instead? Discuss pros and cons.

Why not use ROW_NUMBER() instead? Discuss pros and cons.

SQLmedium0.4 min read

**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...

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Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Bitwise
Key Concepts Tested
partition

Why This Question Matters

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.

How to Approach This

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.

Expert Answer
87 words

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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