Top N per Group — Solution & ExplanationProblems / Top N per Group / EditorialApproachTop-N-per-group is one of the most common window function interview questions.

Rank: Use ROW_NUMBER() partitioned by category, ordered by rating DESC to assign a sequential rank within each category.

Filter: Use a CTE (or subquery) and filter WHERE rank <= 3 to keep only the top 3.

Why CTE: Window functions cannot be used in WHERE clauses directly, so you must compute the rank in one step and filter in another.

If you wanted to include all ties at the boundary, you would use RANK() instead of ROW_NUMBER().Hints

This is the classic Top-N-per-group pattern: rank + filter.

ROW_NUMBER guarantees exactly N rows per group even with ties.

You cannot filter on a window function in the same SELECT — use a CTE or subquery.

Solve Top N per Group yourself →