题解 | #每类视频近一个月的转发量/率#

select tag,sum(if_retweet) as retweet_cut,round(sum(if_retweet)/count(tag),3) as retweet_rate
from (select tag,a.video_id,if_retweet from tb_user_video_log a left join tb_video_info b on a.video_id=b.video_id
where datediff((select max(start_time) from tb_user_video_log),a.start_time)<=29) as t1
group by tag
order by retweet_rate desc