题解 | #每篇文章同一时刻最大在看人数#

select artical_id,max(num) from(
select artical_id,sum(n) over(partition by artical_id order by t,n desc) num
#默认是从第一行开始
from(
select artical_id,in_time t,  1 n from tb_user_log
union all 
select artical_id,out_time t,-1 n from tb_user_log
) a
where artical_id!=0 
)b
group by artical_id
order by max(num) desc
#默认排序是asc