题解 | #每篇文章同一时刻最大在看人数#

select artical_id, max(viewer_ins) max_uv #先列出需要的列 from(select artical_id, sum(diff) over(partition by artical_id order by dt, diff desc)
viewer_ins ###是partition by且和order by之间没有，连接##diff desc 能够满足先算in再算out from( select artical_id, in_time dt, 1 diff ###所有的in_time都会被算作1记录 from tb_user_log where artical_id != 0 union all ###利用union all 会保留全部的数据，这样sum（diff）就可以直接算出人数 select artical_id, out_time dt, -1 diff 两个表格之间的列都要相同且不需要用（）修饰 from tb_user_log where artical_id != 0)a )b group by artical_id order by max_uv desc;