题解 | #每类视频近一个月的转发量/率#

这个题还是比较简单，给的条件比较清晰，就不过多说明。不像上一组题有些题描述不清晰，上一组题不知道是牛客自己出的还是kiang来的。

select
    d.tag,
    sum(a.if_retweet) as retweet_cut,
    format(sum(a.if_retweet)/count(1),3) as retweet_rate
from tb_user_video_log a 
    join (select max(b.start_time) as start_time from tb_user_video_log b) c 
    on date_format(a.start_time,"%Y%m%d") >= date_format(date_sub(c.start_time,interval 29 day),'%Y%m%d')
    join tb_video_info d on a.video_id = d.video_id

group by d.tag
order by retweet_rate desc