How many tracks are in the playlist "movies"?
SELECT count ( * )  FROM tracks AS T1 JOIN playlist_tracks AS T2 ON T1.id  =  T2.track_id JOIN playlists AS T3 ON T3.id  =  T2.playlist_id WHERE T3.name  =  "Movies"
number of tracks in the playlist 'movies' refers to COUNT(*); tracks are related to playlists through a many-to-many relationship involving a join table (playlist_tracks);