题解 | #每篇文章同一时刻最大在看人数#

select
    artical_id,
    max(instant_viewer_cnt) max_uv
from (
    SELECT
    artical_id,
    dt,
    sum(diff) over (partition by artical_id order by dt,diff desc)instant_viewer_cnt
FROM (
    SELECT
        artical_id,
        in_time AS dt,
        1 AS diff
    FROM
        tb_user_log
    WHERE
        artical_id != 0
    UNION ALL
    SELECT
        artical_id,
        out_time AS dt,
        -1 AS diff
    FROM
        tb_user_log
    WHERE
        artical_id != 0
) AS t
)t2
group by 1
order by 2 desc

难哦 下次还不会