Instruction
Good job! That query was really challenging!
It's time to wrap things up. What have we learned in this part?
- It's impossible to put a CTE inside another CTE. However, each CTE can use previously-defined CTEs in the
FROMclause. - Nested CTEs can 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?
Exercise
Click to continue.



