SELECT a.cid,a.play_cnt pv,a.time_len FROM( SELECT t1.cid, COUNT(*) play_cnt, SUM(timestampdiff(minute,t2.start_time,t2.end_time)) time_len, DENSE_RANK() OVER(order by COUNT(*) DESC,SUM(timestampdiff(minute,t2.start_time,t2.end_time)) DESC) ranking FROM course...