Sql server 如果记录不存在，则插入到表中

由于某些原因，这给了我“无法将重复记录插入表”错误

奇怪的是，我做了这样的测试：

DECLARE @CreditDebitAdjustmentDetail TABLE
        (
         CustomerID INT,
         AdjustmentReason VARCHAR(50)
        )

INSERT  INTO @CreditDebitAdjustmentDetail
        (CustomerID, AdjustmentReason)
VALUES  (143, -- CustomerID - int
         '024'  -- AdjustmentReason - varchar(50)
         )

INSERT  INTO [DMS].[dbo].[Deductions]
        (
         CustomerID,
         DeductionCode,
         DeductionDescription
        )
        SELECT  b.CustomerID,
                b.AdjustmentReason,
                b.AdjustmentReason
        FROM    @CreditDebitAdjustmentDetail b
        WHERE   NOT EXISTS ( SELECT 1
                             FROM   [DMS].[dbo].[Deductions]
                             WHERE  CustomerID = b.CustomerID
                                    AND DeductionCode = b.AdjustmentReason )

并且它不会插入到表中，因为记录已经存在

我是不是遗漏了什么

编辑-我以为这样做已经修复了它，但我仍然得到相同的错误：

INSERT  INTO [DMS].[dbo].[Deductions]
        (
         CustomerID,
         DeductionCode,
         DeductionDescription
        )
        SELECT  a.CustomerID,
                a.AdjustmentReason,
                a.AdjustmentReason
        FROM    @CreditDebitAdjustmentDetail a
        WHERE   NOT EXISTS ( SELECT 1
                             FROM   [DMS].[dbo].[Deductions] b
                             WHERE  a.CustomerID = b.CustomerID
                                    AND a.AdjustmentReason = b.DeductionCode )

我想出来了，DOH

关键词。。。明显的-_-

INSERT INTO [DMS].[dbo].[Deductions]
                    (
                     CustomerID,
                     DeductionCode,
                     DeductionDescription
                    )
                    SELECT  DISTINCT
                            a.CustomerID,
                            ISNULL(a.AdjustmentReason, 'UNKNOWN'),
                            ISNULL(a.AdjustmentReason, 'UNKNOWN')
                    FROM    @CreditDebitAdjustmentDetail a
                    WHERE   NOT EXISTS ( SELECT 1
                                         FROM   [DMS].[dbo].[Deductions] b
                                         WHERE  a.CustomerID = b.CustomerID
                                                AND CASE a.AdjustmentReason
                                                      WHEN NULL THEN 'UNKNOWN'
                                                      WHEN '' THEN 'UNKNOWN'
                                                    END = b.DeductionCode )

---

查看您的索引在

扣减

表或用于更新的表中显示

客户ID

或

扣减代码

为

空

。允许一个

NULL

，但不能有多个

NULL

s。PK中有哪些列？扣减表上的CustomerID和DecretionCode=unique。我想我发现了问题。插入时CustomerID为NULL。我一弄明白就回来报到。

INSERT INTO [DMS].[dbo].[Deductions]
                    (
                     CustomerID,
                     DeductionCode,
                     DeductionDescription
                    )
                    SELECT  DISTINCT
                            a.CustomerID,
                            ISNULL(a.AdjustmentReason, 'UNKNOWN'),
                            ISNULL(a.AdjustmentReason, 'UNKNOWN')
                    FROM    @CreditDebitAdjustmentDetail a
                    WHERE   NOT EXISTS ( SELECT 1
                                         FROM   [DMS].[dbo].[Deductions] b
                                         WHERE  a.CustomerID = b.CustomerID
                                                AND CASE a.AdjustmentReason
                                                      WHEN NULL THEN 'UNKNOWN'
                                                      WHEN '' THEN 'UNKNOWN'
                                                    END = b.DeductionCode )