"Find the Top 3" Is Never About Sorting

Concepts covered: sqlRowNumber

When an interviewer says 'top 3 highest-paid employees,' a brand-new candidate hears 'ORDER BY salary DESC LIMIT 3.' That answers a different question. ORDER BY LIMIT gives you the top 3 in the entire company. The interviewer asked for the top 3 in each department. Those are not the same. If your company has one wildly overpaid team, every result will come from that team and every other department will be invisible. What the interviewer is actually testing This question lives in nearly every SQL screen because it separates candidates in seconds. Reading the prompt carefully and saying 'this is a top-N-per-group question, I'll partition by department and use ROW_NUMBER' signals three things at once: you read carefully, you know the pattern, and you reach for window functions. Writing ORDER

About This Interactive Section

This section is part of the Top N Per Group: Beginner 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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DataDriven combines four interview rounds (SQL, Python, Data Modeling, Pipeline Architecture) with adaptive difficulty and spaced repetition. Easy problems get harder as you improve. Weak concepts resurface until you master them. Your readiness score tracks progress across every topic interviewers test. Every lesson section ends with problems you solve by writing and running real code, not by picking multiple-choice answers.