select date(in_time) as dt,
round(sum(timestampdiff(second,in_time,out_time))/count(distinct uid),1) as avg_viiew_len_sec
from tb_user_log
where year(in_time)=2021 and month(in_time)=11 and artical_id >0
group by date(in_time)
order by avg_viiew_len_sec

中规中矩的题目