sql - 从开始和结束日期列计算每天的活跃用户数

Question

我有如下表，我想创建一个每天唯一活跃用户的视图。每个用户都有一个开始和结束日期，但有些日子是重叠的。我该如何解决这个问题？

Answer 1

您可以取消透视数据并使用聚合和窗口函数。这看起来像：

select dte, sum(inc) as change_on_day,
       sum(sum(inc)) over (order by dte) as active_on_day
from ((select user, start_date as dte, 1 as inc from t) union all
      (select user, end_date, -1 from t)
     ) t
group by dte
order by dte;