题解 | #2021年11月每天的人均浏览文章时长#

select t.date,round(sum(t.duration)/count(distinct t.uid),1) as avg_viiew_len_sec
from
(select uid,substr(in_time,1,10) as date,artical_id,timestampdiff(second,in_time,out_time) as duration
from tb_user_log
where month(in_time)=11 and artical_id !=0)t
group by t.date
order by avg_viiew_len_sec

我也不知道为什么要用子查询，但是习惯了