Database: soccer_2
Question: Find the names of states that have some college students playing in the mid position but not in the goalie position.
SQL: 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'