CTE in SQL — a Common Table Expression introduced with WITH — is how you turn a brittle wall of nested subqueries into a readable, debuggable pipeline. In data engineering interviews — the same lanes as basic sql interview questions , joins in sql interview questions , and sql interview questions with answers rounds — reviewers use CTEs as a readability signal: if you can name intermediate results and chain them cleanly, you will survive the live whiteboard refactor.

You will build the pattern from scratch: single-CTE anatomy, chained CTE pipelines, CTE + sql window functions for rank-then-filter (top‑N per group), WITH RECURSIVE org-chart and counting sequences, and the classic board question triad ( CTE vs subquery vs temporary table ) with blunt trade-offs.…