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...