How many users did not leave a review?
select name from useracct where u_id not in ( select u_id from review )
Can you list out their names?
select name from useracct where u_id not in ( select u_id from review )
And the users who did not?
select name from useracct where u_id not in ( select u_id from review )
How many reviews did we receive?
select count ( * ) from review
How many of the reviews have a rating greater than or equal to 5?
select count ( * ) from review where rating > = 5