SELECT tag, sum(if_retweet) as retweet_cut, FORMAT(sum(if_retweet)/count(*),3) AS retweet_rate
FROM tb_user_video_log a
join tb_video_info b ON a.video_id=b.video_id
WHERE datediff('2021-10-02 00:00:00',start_time)<=30
GROUP BY tag
ORDER BY retweet_rate desc