How many of the directors have more than 1 film?
SELECT count ( distinct T1.director )  FROM Movie AS T1 JOIN Movie AS T2 ON T1.director   =   T2.director WHERE T1.title ! =  T2.title
directors with more than 1 film refers to COUNT(DISTINCT director) WHERE there are at least two different movies (T1.title != T2.title) by the same director.