对两个表中不相关的列求和，然后根据 ID 连接

Question

我有两个表基本上是这样设置的（非常精简的版本）：

表 1：

ID       Amt 1     Amt 2
-------------------------    
112     $20        $30
112     $50        $60
125     $75        $05

表 2：

ID       Amt 3     Amt 4
-------------------------
112       $25       $30
125       $40       $60
125      $110      $120

所有金额列需要单独求和，输出类似于：

查询结果：

ID       Amt 1     Amt 2     Amt 3     Amt 4
--------------------------------------------
112     $70        $90       $25       $30
125     $75        $05       $150      $180

我尝试过的连接导致记录重复（和求和）的倍数是 ID 在第二个表中重复的次数。我没有连接这些表的主键。

任何帮助将不胜感激。

谢谢！

Answer 1

在 SQL Server 2005 或更高版本上，您可以使用两个 CTE（通用表表达式）对每个表进行求和/分组，然后将两者连接起来 - 如下所示：

;WITH CTE1 AS
(
    SELECT 
        ID, Amount1 = SUM(Amt1), Amount2 = SUM(Amt2)
    FROM
        dbo.SumTbl1
    GROUP BY
        ID  
),
CTE2 AS
(
    SELECT 
        ID, Amount3 = SUM(Amt3), Amount4 = SUM(Amt4)
    FROM
        dbo.SumTbl2
    GROUP BY
        ID  
)
SELECT CTE1.ID, Amount1, Amount2, Amount3, Amount4
FROM CTE1
INNER JOIN CTE2 ON CTE1.ID = CTE2.ID

这给了我你想要的输出

Answer 2

要正确解决此问题，您需要单独进行聚合。即使两个表都具有相同 id 的多行，这也可以工作：

select id, sum(amt1), sum(amt2), sum(amt3), sum(amt4)
from ((select id, sum(amt1) as amt1, sum(amt2) as amt2, NULL as amt3, NULL as amt4
       from tbl1
       group by id
      ) union all
      (select id, NULL, NULL, sum(amt3), sum(amt4)
       from tbl2
       group by id
      )
     ) t
group by id

上面的查询用group by 给出了这个想法。为此，有些人更喜欢full outer join：

select coalesce(t1.id, t2.id) as id, amt1, amt2, amt3, amt4
from (select id, sum(amt1) as amt1, sum(amt2) as amt2
       from tbl1
       group by id
      ) t1 full outer join
      (select id, sum(amt3) as amt3, sum(amt4) as amt4
       from tbl2
       group by id
      ) t2
      on t1.id = t2.id

关键是聚合必须在任何连接之前完成，这样就不会有多行的问题。