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SQL Window Function Interview Questions
Window function questions test how you compute row-level metrics while keeping the original rows.
Expect ROW_NUMBER, RANK, LAG, LEAD, and running totals with PARTITION BY and ORDER BY.
Interviewers want clear reasoning about partitions, ordering, and edge cases.
53Questions
21Companies
Common SQL window function interview patterns
- Top N per group using ROW_NUMBER
- Running totals and cumulative sums
- LAG/LEAD for previous and next values
- Ranking ties with RANK vs DENSE_RANK
- Window + aggregation combinations
- Moving averages over time windows
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Common mistakes with SQL window functions
- Missing PARTITION BY or ORDER BY
- Using RANK when ROW_NUMBER is required
- Incorrect window frames for running metrics
- Combining aggregates and windows incorrectly
- Ignoring NULL ordering behavior
How window function questions are evaluated in interviews
Interviewers prioritize correctness and the right partitioning logic.
Explain why you chose a window function instead of a GROUP BY.
Be clear about ordering and how ties are handled.