select tag,sum(if_retweet) retweet_cnt,round(sum(if_retweet)/count(*),3) retweet_rate
from tb_user_video_log tl left join tb_video_info ti on tl.video_id = ti.video_id
where timestampdiff(day,start_time,(select max(start_time) from tb_user_video_log))<=29
group by tag
order by retweet_rate desc