SELECT count(*) FROM tryout WHERE pPos  =  'goalie'
How many students whose are playing the role of goalie?
[Schema (values) (types)]: | soccer_2 |  College : cname (text) , state (text) , enr (text) | Player : pid (text) , pname (text) , ycard (text) , hs (number) | Tryout : pid (text) , cname (text) , ppos (text) , decision (number);