题解 | #每类视频近一个月的转发量/率#

select
    tag,
    sum(if_retweet),
    round(sum(if_retweet) / count(tag), 3) as zfl
from
    tb_user_video_log a
    join tb_video_info b on a.video_id = b.video_id
where
    start_time <=(
        select max(start_time) from tb_user_video_log
    ) and start_time>date_sub((
        select max(start_time) from tb_user_video_log
    ),interval 30 day)
group by
    tag
order by zfl desc