在if陳述句中參考資料庫

在我的 Django-Python 應用程式中實作它之前，我目前正在通過 SQL Server Management Studio 查詢運行以下代碼。

在 if 陳述句開始之前，我無法弄清楚如何參考相關資料庫：

詢問：

If Age1 IS NULL 
    set @Current = DCBalance
    Select Account, Name, E-mail , Age1 , Age2 , Age3 , Age4 , Age5 , @Current ,DCBalance from [Graceland Estates BC].[dbo].[_avCustomerAging]
Else  Age1 IS NOT NULL
    If UADebit <> '0' and DCBalance > 0 
        Set @Current = DCBal - Sum(Age1, Age2, Age3 , Age4, Age5)
        Select Account , Name , E-mail , Age1 , Age2 , Age3 , Age4 , Age5 , @Current , DCBalance from [Graceland Estates BC].[dbo].[_avCustomerAging]
    Else  UADebit = '0'  and DCBalance < 0 
        Set @Age1X = fForeignBalance   Age1 - FCAge1
        Set @Age2X = fForeignBalance   Age2 - FCAge2
        Set @Age3X = fForeignBalance   Age3 - FCAge3
        Set @Age4X = fForeignBalance   Age4 - FCAge4
        Set @Age5X = fForeignBalance   Age5 - FCAge5
        Set @Current = 0
        Select Account , Name , E-mail , @Age1X , @Age2X , @Age3X , @Age4X , @Age5X , @Current , DCBalance
    Else  UADebit = '0'  and DCBalance > 0 
        Set @Ages = '0'
        Select Account , Name , E-mail , @Ages , @Ages , @Ages , @Ages , @Ages , DCBalance as Current , DCBalance

在上面的代碼中，它的目的是確定資料是否與 if 陳述句中表示的內容相匹配，并根據資料的顯示方式進行計算。

這是我在包含 CASE 陳述句的情況下嘗試相同操作時的代碼：

Select Account, Name , EMail, Age1 AS Cur, Age2 , Age3 , Age4, Age5 ,DCBalance,
Case 
    When AccountLink = NULL Then Age1 = DCBalance and Age2 = 0 and Age3 = 0 and Age4 = 0 and Age5= 0
    When UADebit <> 0 and DCBalance > 0 Then Age1 = DCBalance - (Age2   Age3   Age4   Age5)
    When UADebit = 0 and DCBalance < 0 Then Age1 = 0 and Age2 = fForeignBalance   Age2 - FCAge2 and Age3 = fForeignBalance   Age3 - FCAge3 and Age4 = fForeignBalance   Age4 - FCAge4 and Age5 = fForeignBalance   Age5 - FCAge5
    When UADebit = 0 and DCBalance > 0 Then Age1 = DCBalance and Age2 = 0 and Age3 = 0 and Age4 = 0 and Age5= 0
End 
From [Kyle].[dbo].[_avCustomerAging]

Incorrect syntax near '='.執行時回傳錯誤

uj5u.com熱心網友回復：

CASEis an expression NOT a statement，在參考官方檔案時明確說明，即單個 case 運算式，無論分支數量如何，都可以回傳單個值。它不允許您運行查詢的條件部分。

此外，您無法NULL與=您使用IS NULL.

我認為以下包含您所針對的相同邏輯，但是現在調整它應該是微不足道的，因為您可以看到哪里出錯了。

SELECT Account, [Name], EMail, Age1, Age2, Age3, Age4, Age5, DCBalance,

    CASE 
        WHEN AccountLink IS NULL THEN DCBalance
        WHEN UADebit <> 0 AND DCBalance > 0 THEN DCBalance - (Age2   Age3   Age4   Age5)
        WHEN UADebit = 0 AND DCBalance < 0 THEN 0
        WHEN UADebit = 0 AND DCBalance > 0 THEN DCBalance
    END AS Age1_New
    ,
    Case 
        WHEN AccountLink IS NULL THEN 0
        WHEN UADebit = 0 AND DCBalance < 0 THEN fForeignBalance   Age2 - FCAge2
        WHEN UADebit = 0 AND DCBalance > 0 THEN 0
    END Age2_New
    ,
    CASE 
        WHEN AccountLink IS NULL Then 0
        WHEN UADebit = 0 AND DCBalance < 0 THEN fForeignBalance   Age3 - FCAge3
        WHEN UADebit = 0 AND DCBalance > 0 THEN 0
    END Age3_New
    ,
    CASE 
        WHEN AccountLink IS NULL THEN 0
        WHEN UADebit = 0 AND DCBalance < 0 THEN fForeignBalance   Age4 - FCAge4
        WHEN UADebit = 0 AND DCBalance > 0 THEN 0
    END Age4_New
    ,
    CASE 
        WHEN AccountLink IS NULL THEN 0
        WHEN UADebit = 0 AND DCBalance < 0 THEN fForeignBalance   Age5 - FCAge5
        WHEN UADebit = 0 AND DCBalance > 0 THEN 0
    END Age5_New

FROM _avCustomerAging;

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