with t1 as( select cid ,score ,start_time ,round(timestampdiff(minute,start_time,end_time),3) len from play_record_tb ) ,t2 as( select cid ,avg(score) avg_score from play_record_tb group by cid ) select t1.cid cid ,count(*) pv ,sum(len) time_len from t1 join t2 on t1.cid=t2.cid join course_info_tb t...