使用 case 语句时的 Group By 子句问题

Question

我试图总结每个不同发件人全年的数量，并将年份作为字段。 我正在使用 case 语句来执行此操作。

select distinct sender,
  case
    when extract(month from (month)) = 1
      then sum(volume)
  end as January,
  case
    when  extract(month from (month)) = 2
      then sum(volume)
  end as February,
  case
    when extract(month from (month)) = 3
      then sum(volume)
  end as March
from [lifetime_data]
group by 1

当我运行这个时，我收到一个错误，要求我按月分组，月份不是我选择的列之一，我只在我的情况下使用它......我该如何解决这个问题？

Answer 1

我认为你想要条件聚合—— case表达式是sum()的一个参数：

select sender,
       sum(case when extract(month from (month)) = 1 then volume end) as January,
       sum(case when extract(month from (month)) = 2 then volume end) as February,
       sum(case when extract(month from (month)) = 3 then volume end) as March
from [lifetime_data]
group by 1

Answer 2

您收到此错误是因为您的 case 语句逐行运行，因此每行的 o/p 与每行的组不匹配。 试试下面

   Select sender, 
  extract(month from (month)), 
    SUM(Volume) from table group by
     sender, 
  extract(month from (month)) having
    extract(month from (month)) IN 
      (1,2,3)