CTEs (WITH clause)

Concepts covered: sqlCte

A CTE is a named result set you define once at the top of a query, then reference by name anywhere below it. This works exactly the way you assign an intermediate variable in code before using it in a calculation. The filter logic lives inside the CTE, the main query reads from the named result, and the two steps stay cleanly separated. If you have ever computed something once to avoid repeating the same expression twice, you already understand what a CTE does. CTE Usage Examples The following examples show how to define and use CTEs, from a single named result set to chaining multiple CTEs together. Basic Example Multiple CTEs You can define several CTEs in a single query, separating them with commas. Each CTE can reference the ones declared before it, allowing you to build complex logic

About This Interactive Section

This section is part of the Query Structure: 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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