题解 | #每类视频近一个月的转发量/率#

select 
    tag,
    sum(if_retweet) retweet_cut,
    round(sum(if_retweet)/count(start_time),3) retweet_rate
from 
    tb_user_video_log u 
left join 
    tb_video_info v
on u.video_id = v.video_id
where date(start_time) > (select date_add(max(date(start_time)),interval -30 day) from tb_user_video_log)
group by tag
order by retweet_rate desc;