What schools have players that tried out for the mid position but not as goalies?
select cname from tryout where ppos = 'mid' except select cname from tryout where ppos = 'goalie'
In which states do those schools reside?
select t1.state from college as t1 join tryout as t2 on t1.cname = t2.cname where t2.ppos = 'mid' except select t1.state from college as t1 join tryout as t2 on t1.cname = t2.cname where t2.ppos = 'goalie'
How many of them exist?
select count(*) from (select t1.state from college as t1 join tryout as t2 on t1.cname = t2.cname where t2.ppos = 'mid' except select t1.state from college as t1 join tryout as t2 on t1.cname = t2.cname where t2.ppos = 'goalie')