题解 | #每类视频近一个月的转发量/率#

select
DISTINCT tag,
sum(if_retweet),
round(sum(if_retweet)/COUNT(a.uid),3)
FROM
tb_user_video_log a
left join
tb_video_info b
on a.video_id = b.video_id
where DATEDIFF(DATE((select max(start_time) FROM tb_user_video_log)), DATE(a.start_time)) <= 29
group by tag
order by round(sum(if_retweet)/COUNT(a.uid),3) desc

第十行是在题解看到的大佬的思路，一开始还以为是牛客网出错了，检查一下发现是自己的问题，没有把时间限制住，所以还是得好好看需求