Among the trains running east, how many trains have at least 4 cars?
east is a direction; at least 4 cars refers to carsNum > = 4
SELECT SUM(CASE WHEN T1.direction = 'east' THEN 1 ELSE 0 END)as count FROM trains AS T1 INNER JOIN ( SELECT train_id, COUNT(id) AS carsNum FROM cars GROUP BY train_id ) AS T2 ON T1.id = T2.train_id WHERE T2.carsNum >= 4
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, 
