Array Cleanup

Real-world arrays often contain duplicates or arrive in unpredictable order. SQL provides functions to normalize arrays for consistent processing and analysis. Deduplication Sorting & Set Operations Sorted arrays enable consistent display and comparison. Note that string sorting is alphabetical, so sizes like S, M, L, XL will not sort in the expected order without custom logic. ARRAY_UNION/INTERSECT Combine arrays from multiple sources using set operations: With array operations and cleanup techniques covered, you are ready to explore the map data structure and its specialized functions.

About This Interactive Section

This section is part of the Complex Data: 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.

How DataDriven Lessons Work

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.