Chained Joins vs Recursive CTE

Concepts covered: sqlRecursiveCte

Recursive CTEs are the canonical tool for unbounded hierarchy traversal in SQL. The shape is the same across engines: an anchor query that produces the starting set, a recursive step that joins the previous iteration's result to the source table, and a UNION ALL that combines them. The engine iterates the recursive step until it returns zero new rows. Understanding the iteration mechanics is what separates a query that ships from one that infinite-loops in production. The canonical recursive CTE Reading the anchor and the recursive step The anchor produces the starting set: the direct reports of employee 42. Each row has depth=1 and a path array containing just its own employee_id. The recursive step joins the source table (employees) to the CTE itself (subtree), matching each next-level e

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This section is part of the Self-Join: Advanced 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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