题解 | 每类视频近一个月的转发量/率

select tag,

       sum(if_retweet) retweet_cnt,

       round(sum(if_retweet)/count(*),3) retweet_rate

from tb_user_video_log l

join tb_video_info i

on l.video_id = i.video_id

where timestampdiff(day,start_time,(select max(start_time) from tb_user_video_log)) < 30

group by tag

order by retweet_rate desc

group by前的where子句不能用聚合函数，但是为什么我用having语句写不出来