题解 | #每类视频近一个月的转发量/率#

SELECT a.tag, SUM(if_retweet) AS retweet_cut, ROUND(SUM(if_retweet) / COUNT(*),3) AS retweet_rate
FROM tb_user_video_log JOIN tb_video_info a USING (video_id)
WHERE start_time >= DATE_SUB((
                             SELECT MAX(start_time)
                             FROM tb_user_video_log
                             ),INTERVAL 30 DAY)
  AND start_time <= (
                    SELECT MAX(start_time)
                    FROM tb_user_video_log
                    )
GROUP BY a.tag
ORDER BY retweet_rate DESC