题解 | #每篇文章同一时刻最大在看人数#
每篇文章同一时刻最大在看人数
http://www.nowcoder.com/practice/fe24c93008b84e9592b35faa15755e48
第一次做到这个类型的题目，一定要收藏一下。 本题的关键点： 1一个时间戳表格，记录每个时间点读者的行为， 2同时根据题目先进后出，对sign进行降序排序 3搭配sum + 窗口函数（order by）是累计和，这也是关键点
select artical_id,max(uv) as max_uv
from (
select artical_id,time,sum(sign) over(partition by artical_id order by time ,sign desc) as uv
FROM
(select artical_id,in_time as time ,1 as sign
from tb_user_log log1 where artical_id!=0
union all
select artical_id,out_time as time ,-1 as sign
from tb_user_log log1 where artical_id!=0) tmp
order by artical_id,time,sign desc
) tmp2
group by artical_id
order by max_uv DESC
