Sql Join 3 Tables 查询贷款总额结果

Question

我必须从 3 个表中获取客户贷款总额，这两个表被给予贷款总和，另一个减去支付的金额，并且这些表具有共同的客户 ID。到目前为止，只有当所有表中都存在客户 ID 时，我才能得到结果，但如果它不存在于一个表中，我将不会在结果中得到客户。或者当我锚定到客户时，我得到了 NULL 客户 ID。

SELECT 
  AS1.C_ID AS [Customer ID],
  ISNULL(AS1.OldCustomerLoan, 0) AS [Old Loan],
  ISNULL(AS2.NewGivenLoan, 0) AS [New Given Loan],
  ISNULL(AS3.LoanPaid, 0) AS [PaidLoanAmount],
  (ISNULL(AS1.OldCustomerLoan, 0) + 
  ISNULL(AS2.NewGivenLoan, 0) - 
  ISNULL(AS3.LoanPaid,0) ) AS Total 
FROM
  Customer C
  LEFT OUTER JOIN
   (SELECT 
       MOC.C_ID,
       SUM(MOC.Quantity) AS OldCustomerLoan 
    FROM 
       Money_On_Customer MOC (NOLOCK)
    GROUP BY 
       MOC.C_ID) AS1 
    ON c.C_Id = AS1.C_Id
   LEFT OUTER JOIN 
(SELECT 
       NGL.C_ID 
       ,SUM(NGL.G_Take_Loan) AS NewGivenLoan 
    FROM 
       Given_Loan NGL   
    GROUP BY 
       NGL.C_ID) AS2
    ON c.C_Id = AS2.C_Id
LEFT OUTER JOIN 
   (SELECT 
       GLP.C_ID, SUM(GLP.G_P_Loan) AS LoanPaid 
    FROM 
       Given_Loan_Paid GLP 
    GROUP BY 
       GLP.C_ID ) AS3
ON c.C_Id = AS3.C_Id

这是我的两个结果的图片：

When I get NULL Customer IDs

When I don't get All the Customers

Answer 1

第一列需要使用 c.c_id

为了只获取它们存在于至少一个表中的记录，您可以将其添加到查询中，只需将当前查询放在点的位置，然后添加 leftid col

Select * 
From
(Select c.c_id custonerid, 
        Coalesce(Coalesce(as1.c_id,as2.c_id),as3.c_id) leftid,......
 From ....
) ilv
Where leftid is not null

你也许可以添加

Where coalesce(coalesce(as1.c_id,as2.c_id),as3.c_id) is not null 

到您的查询结束

Answer 2

@Ab Bennett 的回答是对的， 因为您应该使用主（主）表的主键列 如果客户 ID 在 as1 (Money_On_Customer) 中不可用，它将显示为空。 希望你能理解我的解释。

更新：

并使用以下获取客户 ID

COALESCE(c.C_Id, AS1.C_Id, AS2.C_Id)

您将首先获得非空客户 ID

Answer 3

在@Ab Bennett 的帮助下，这是我的答案

Select * 
  From
  ( 
   SELECT 
     C.C_Name AS [Customer ID],
     ISNULL(AS1.OldCustomerLoan, 0) AS [Old Loan],
     ISNULL(AS2.NewGivenLoan, 0) AS [New Given Loan],
     ISNULL(AS3.LoanPaid, 0) AS [PaidLoanAmount],
     (ISNULL(AS1.OldCustomerLoan, 0) + 
     ISNULL(AS2.NewGivenLoan, 0) - 
     ISNULL(AS3.LoanPaid,0) ) AS Total 
   FROM
    Customer C
    LEFT OUTER JOIN
     (SELECT 
        MOC.C_ID,
        SUM(MOC.Quantity) AS OldCustomerLoan 
   FROM 
       Money_On_Customer MOC (NOLOCK)
    GROUP BY 
       MOC.C_ID) AS1 
    ON c.C_Id = AS1.C_Id
   LEFT OUTER JOIN 
     (SELECT 
       NGL.C_ID 
       ,SUM(NGL.G_Take_Loan) AS NewGivenLoan 
       FROM 
       Given_Loan NGL   
    GROUP BY 
    NGL.C_ID) AS2
    ON c.C_Id = AS2.C_Id
    LEFT OUTER JOIN 
     (SELECT 
       GLP.C_ID, SUM(GLP.G_P_Loan) AS LoanPaid 
    FROM 
       Given_Loan_Paid GLP 
    GROUP BY 
       GLP.C_ID ) AS3
   ON c.C_Id = AS3.C_Id) ilv
   Where not ([Old Loan] = 0 and [New Given Loan]=0 and PaidLoanAmount =0 )