仅对Sql Server中的不同行求和

我有四个表，其中第一个表与其余三个表（分别命名为Second、Third、Fourth）有一对多的关系。我只想对select查询返回的不同行求和。这是我的查询，到目前为止我一直在尝试

select count(distinct First.Order_id) as [No.Of Orders],sum( First.Amount) as [Amount] from First 
inner join Second  on First.Order_id=Second.Order_id
inner  join Third  on Third.Order_id=Second.Order_id
inner  join  Fourth  on Fourth.Order_id=Third.Order_id

此查询的结果是：

No.Of Orders                       Amount
7                                  69

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但是这个数量应该是49，因为第一列的数量之和是49，但是由于内部联接和一对多关系，它会计算重复行的数量之和。如何避免这种情况。请指导我。我认为问题是给定id的联接中的笛卡尔积。您可以使用行数解决这个问题：

顺便说一句，您也可以在where子句中使用条件来表示这一点，因为您似乎只将联接用于过滤：

select count(First.Order_id) as [No.Of Orders], sum(First.Amount) as [Amount]
from First
where exists (select 1 from second where First.Order_id=Second.Order_id) and
      exists (select 1 from third where First.Order_id=third.Order_id) and
      exists (select 1 from fourth where First.Order_id=fourth.Order_id);

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谢谢，您的第一个查询给了我错误。无法绑定多部分标识符first.Order\u id。

select count(First.Order_id) as [No.Of Orders], sum(First.Amount) as [Amount]
from First
where exists (select 1 from second where First.Order_id=Second.Order_id) and
      exists (select 1 from third where First.Order_id=third.Order_id) and
      exists (select 1 from fourth where First.Order_id=fourth.Order_id);