
Function COUNT
Function AVG
Functions SUM, MAX, MIN


Good! Of course, you can use COUNT(*), COUNT(column), or COUNT(expression) with GROUP BY.


For each client, show their client_id and the number of projects commissioned by that specific client which have some feedback (zero if there are no such projects). Name the second column projects_no.

Stuck? Here's a hint!

Remember to use COUNT(feedback) instead of COUNT(*).