题解 | 每类视频近一个月的转发量/率

SELECT
    tag,
    SUM(if_retweet) AS retweet_cnt,
    ROUND(AVG(if_retweet), 3) AS retweet_rate
FROM
    tb_user_video_log
    JOIN tb_video_info USING (video_id)
WHERE
    DATEDIFF(
        (
            SELECT
                MAX(DATE(start_time))
            FROM
                tb_user_video_log
        ),
        DATE(start_time)
    ) <= 29
GROUP BY
    tag
ORDER BY
    retweet_rate DESC