题解 | 每类视频近一个月的转发量/率
select tag, sum(if_retweet) retweet_cnt, round(avg(if(if_retweet=1,1,0)),3) retweet_rate from tb_user_video_log tu left join tb_video_info tv on tu.video_id = tv.video_id where timestampdiff(day,date(start_time),date((select max(start_time) from tb_user_video_log))) < 30 group by tag order by retweet_rate desc