Introduction
Nested CTEs
Summary
12. Summary

## Instruction

Good job! This query was really challenging!

It's time to wrap things up.

• It's impossible to put a CTE inside another CTE. However, each CTE might use previously defined CTEs in the FROM clause.
• Nested CTEs might be used to compute aggregate functions on a few levels.
• If you need more than just the aggregate result in the outer query, you can use a small subquery.
• CTEs can also be used to compare two (or more) groups of rows.

Are you ready for a short quiz, then?

## Exercise

Press to continue.