The ROW_NUMBER + Filter Trick

Concepts covered: sqlRankDenseRank

The shape of the question rarely changes. 'Top 3 highest-paid employees per department.' 'Top 5 best-selling products per category.' 'Top 10 most-recent orders per customer.' What changes is what 'top 3' actually means when the data does not cooperate. Two employees tied for second place. A category with only two products. A NULL salary on a row that should be ignored. Every one of those edge cases changes the right query. The interviewer at this level is watching whether you anticipate the edge case and pick the right tool, or whether you write ROW_NUMBER by reflex and have to be corrected. What the interviewer is actually testing The clarifying question that earns the credit Before you write SELECT, ask: 'should ties at position N be included or excluded, and is the report counting disti

About This Interactive Section

This section is part of the Top N Per Group: Intermediate lesson on DataDriven, a free data engineering interview prep platform. Each section includes explanations, worked examples, and hands-on code challenges that execute in real time. SQL queries run against a live database. Python runs in a sandboxed Docker container. Data modeling problems validate against interactive schema canvases. All content is framed around what data engineering interviewers actually test at companies like Meta, Google, Amazon, Netflix, Stripe, and Databricks.

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