有条件地加入两个或多个表

问题描述

我创建了一个视图来连接三个表SUMDEPOSITES，SUMWITHDRAWALS和SUMLOANS

在SUMDEPOSITES中我有

i have created a view to join three tables SUMDEPOSITES,SUMWITHDRAWALS and SUMLOANS
In SUMDEPOSITES i have

SELECT DISTINCT AccountNumber, SUM(Amount) AS deposites
FROM         dbo.DepositeDetails
GROUP BY AccountNumber

在SUMWITHDRAWS中的
我有

in SUMWITHDRAWALS i have

SELECT DISTINCT AccountNumber, SUM(Amount) AS withdrawals
FROM         dbo.WithdrawalDetails
GROUP BY AccountNumber

SUMLOANS的
我有

in SUMLOANS i have

SELECT DISTINCT AccountNumber, SUM(TotRepayment) AS Loans
FROM         dbo.Loans
GROUP BY AccountNumber

现在我已经创建了第三个视图BALANCE来做这个计算

now i have created a third view BALANCE which is to do this calculation

SELECT     dbo.SUMDEPOSITES.AccountNumber, dbo.SUMDEPOSITES.deposites - dbo.SUMWITHDRAWALS.withdrawals - dbo.SUMLOANS.Loans AS Balance
FROM         dbo.SUMDEPOSITES LEFT OUTER JOIN
                      dbo.SUMWITHDRAWALS ON dbo.SUMWITHDRAWALS.AccountNumber = dbo.SUMDEPOSITES.AccountNumber LEFT OUTER JOIN
                      dbo.SUMLOANS ON dbo.SUMLOANS.AccountNumber = dbo.SUMWITHDRAWALS.AccountNumber

但问题是当SUMDEPOSITES或SUMLOANS中没有数据并且有数据时在SUMDEPOSITES中，它rturns null而不是SUMDEPOSITES中的数据。

当桌面为空时我没有得到正确答案。

有人能帮助我吗？

But the problem is when there is no data in SUMDEPOSITES or SUMLOANS and there is data in SUMDEPOSITES, it rturns null instead of the data in SUMDEPOSITES.
When on table is empty i do not get a correct answer.
Can someone help me?

推荐答案

SELECT     dbo.SUMDEPOSITES.AccountNumber, isnull(dbo.SUMDEPOSITES.deposites,0) -
    isnull(dbo.SUMWITHDRAWALS.withdrawals,0) - isnull(dbo.SUMLOANS.Loans,0) AS Balance
FROM         dbo.SUMDEPOSITES LEFT OUTER JOIN
                      dbo.SUMWITHDRAWALS ON dbo.SUMWITHDRAWALS.AccountNumber = dbo.SUMDEPOSITES.AccountNumber LEFT OUTER JOIN
                      dbo.SUMLOANS ON dbo.SUMLOANS.AccountNumber = dbo.SUMWITHDRAWALS.AccountNumber

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