Among the trains running west, how many trains have no more than one car with an open roof?
running west refers to direction = 'west'; open roof refers to roof = 'none'
SELECT SUM(CASE WHEN T1.direction = 'west' THEN 1 ELSE 0 END)as count FROM trains AS T1 INNER JOIN ( SELECT train_id, COUNT(id) FROM cars WHERE roof = 'none' GROUP BY train_id HAVING COUNT(id) = 1 ) AS T2 ON T1.id = T2.train_id 
database name:db_id trains
cars table cars Cols: id dtype integer, train id dtype integer, position dtype integer, shape dtype text, length dtype text, sides dtype text, roof dtype text, wheels dtype integer, load_shape dtype text, load number dtype integer, 
trains table trains Cols: id dtype integer, direction dtype text, 
