题解 | #每类视频近一个月的转发量/率#

select info.tag,sum(log.if_retweet) as retweet_cut,
       round((sum(log.if_retweet)/count(info.tag)),3) as retweet_rate
from tb_video_info info right join tb_user_video_log log
    on info.video_id = log.video_id
where DATEDIFF(DATE((select max(start_time) from tb_user_video_log)) ,DATE(start_time)) <= 29
group by info.tag
order by retweet_cut desc