What are the names of all the states with college students playing in the mid position but no goalies?
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'