# 问题:计算2021年里有播放记录的每个视频的完播率(结果保留三位小数),并按完播率降序排序 select t1.video_id, round(sum(if(timestampdiff(second,t1.start_time,t1.end_time)>=t2.duration,1,0))/count(t2.video_id),3) as avg_rate from tb_user_video_log t1 inner join...