Database: soccer_2
Question: What is the count of states with college students playing in the mid position but not as goalies?
SQL: 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')