题解 | 2021年11月每天的人均浏览文章时长

SELECT date dt, 
    ROUND(SUM(watch_time)/COUNT(DISTINCT uid),1)  avg_viiew_len_sec
FROM(
    SELECT uid, artical_id, 
    timestampdiff(SECOND,in_time,out_time) watch_time,
    DATE(out_time) date
    FROM tb_user_log
    WHERE artical_id != 0 AND YEAR(out_time) = 2021 AND MONTH(out_time) = 11
) co 
GROUP BY dt
ORDER BY 2