select date_format(in_time,'%Y-%m-%d') dt,
round(sum(timestampdiff(second,in_time,out_time))/count(distinct uid),1) avg_viiew_len_sec
from tb_user_log
where date_format(in_time,'%Y-%m')='2021-11' and artical_id  != 0
group by date_format(in_time,'%Y-%m-%d')
order by avg_viiew_len_sec asc;