select substr(in_time,1,10) as dt, round(sum(TIMESTAMPDIFF(SECOND, in_time, out_time)) / count(distinct uid), 1) as avg_viiew_len_sec from tb_user_log where substr(in_time,1,7) = '2021-11' and artical_id != 0 group by substr(in_time,1,10) order by round(sum(TIMESTAMPDIFF(SECOND, in_time, out_time)) ...