题解 | #每篇文章同一时刻最大在看人数#

select artical_id,max(maxz)
from
    (
        select artical_id,dt,sum(diff)OVER(PARTITION BY artical_id ORDER BY dt,diff desc) maxz
        from 
            (
                SELECT artical_id,in_time dt,1 diff
                FROM tb_user_log
                WHERE artical_id != 0
                UNION ALL
                SELECT artical_id,out_time dt,-1 diff
                FROM tb_user_log
                WHERE artical_id != 0
                order by 1,2
            ) t1
    ) t2
group by 1
order by 2 desc