select tag,sum(if_retweet) as cnt,round(sum(if_retweet)/count(1),3) as rate from tb_user_video_log join tb_video_info using (video_id) where datediff(date((select max(start_time) from tb_user_video_log )),date(start_time))<30 group by tag order by rate desc; 看懂题目才是关键,大无语没事干练习一下上来题目给我干碎了建议下次把图表塞进例...