Maps in SQL

A map is a collection of key-value pairs where each key maps to exactly one value. Maps are also called dictionaries or associative arrays in other contexts. In SQL, maps provide a way to store flexible, named attributes without defining a fixed schema. Maps are particularly valuable for storing metadata, configuration settings, or properties that vary between rows. Instead of adding nullable columns for every possible attribute, you store them all in a single map column. Map Basics Accessing Map Values Retrieve values from a map using bracket notation with the key: Comparison & Use Cases Map Use Cases

About This Interactive Section

This section is part of the Complex Data: 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 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.