题解 | #每类视频近一个月的转发量/率#

select
    t2.tag,
    sum(if_retweet) as retweet_cut,
    round(sum(if_retweet) / count(1), 3) as retweet_rate
from
    tb_user_video_log t1
    join tb_video_info t2 on t1.video_id = t2.video_id
where
    datediff (
        (
            select
                max(start_time)
            from
                tb_user_video_log
        ),
        t1.start_time
    ) <= 29
group by
    t2.tag
order by
    retweet_rate desc;