What is the name of the activity with the most students?
create table participates_in (actid varchar, PRIMARY KEY (actid)); create table activity (activity_name varchar, actid varchar, PRIMARY KEY (activity_name))
select t1.activity_name from activity as t1 join participates_in as t2 on t1.actid = t2.actid group by t1.actid order by count(*) desc limit 1