题解 | #每类视频近一个月的转发量/率#

select tvi.tag, 
sum(tuvl.if_retweet) retweet_cut, 
round(avg(tuvl.if_retweet),3) retweet_rate
from tb_video_info tvi
inner join
tb_user_video_log tuvl
on tvi.video_id=tuvl.video_id
where timestampdiff(day,start_time,(select max(start_time) from tb_user_video_log))<=29
group by tvi.tag
order by retweet_rate desc

• 点击数直接用sum
• 点击率用avg
• 注意读懂题目的时间要求是最近一次互动的时间，然后再往前推30天的这一段时间