How many coaches does each club has? List the club id, name and the number of coaches.
create table club (club_id varchar, club_name varchar, PRIMARY KEY (club_id)); create table coach (club_id varchar, PRIMARY KEY (club_id))
select t1.club_id, t1.club_name, count(*) from club as t1 join coach as t2 on t1.club_id = t2.club_id group by t1.club_id