Table schema:
CREATE TABLE tryout (cName VARCHAR, pPos VARCHAR); CREATE TABLE college (state VARCHAR, cName VARCHAR)

Question: How many states that have some college students playing in the mid position but not in the goalie position.
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')