FIRST, LAST, NTH VALUE

Concepts covered: sqlFirstLastValue

Positional Function Basics Each positional function accesses a specific row within the window frame. Understanding their syntax and default behaviors is essential for correct usage. FIRST_VALUE Every employee can see how far their salary is from the highest in their department. The person with the top salary has a gap of zero. This pattern is commonly used in compensation analysis to show each employee their relative position without revealing other individuals' exact salaries. The LAST_VALUE Frame Trap NTH_VALUE

About This Interactive Section

This section is part of the Window Functions: 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 PostgreSQL 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.