How many distinct hometowns are there?
select count(distinct hometown) from people
How many gymnasts are from each town?
select t2.hometown, count(*) from gymnast as t1 join people as t2 on t1.gymnast_id = t2.people_id group by t2.hometown
What is the most common hometown?
select t2.hometown from gymnast as t1 join people as t2 on t1.gymnast_id = t2.people_id group by t2.hometown order by count(*) desc limit 1