Subqueries and Common Table Expressions

In this lesson we look closely at subqueries and common table expressions, and how it fits into the wider practice of SQL.

We start with the underlying idea, then move to a concrete example, and finish with the mistakes people most often make so you can recognise them early in your own work.

Work through the material at your own pace. If anything is unclear, revisit the previous lesson before moving on, since each section builds on the one before it.