How many stadiums are there?
select count ( * ) from stadium
How many games has each stadium held?
select t1.id, count ( * ) from stadium as t1 join game as t2 on t1.id = t2.stadium_id group by t1.id
What is the total attendance of each stadium?
select t1.id, sum ( total_attendance ) from stadium as t1 join game as t2 on t1.id = t2.stadium_id group by t1.id