Question

我有合并声明

DESTINMATION TABLE = ~DST SOURCE TABLE = ~SRC

MERGE DST
USING (SELECT * FROM SRC WHERE <Some_Condition>) SRC
ON SCR.COL1 = DST.COL1 OR (SRC.COL1 IS NULL AND DST.COl1 IS NULL) AND 
ON SCR.COL2 = DST.COL2 OR (SRC.COL2 IS NULL AND DST.COl2 IS NULL) AND 
ON SCR.COL3 = DST.COL3 OR (SRC.COL3 IS NULL AND DST.COl3 IS NULL) AND 
ON SCR.COL4 = DST.COL4 OR (SRC.COL4 IS NULL AND DST.COl4 IS NULL) 
WHEN MATCHED UPDATE DST
WHEN NOT MATCHED BY SOURCE THEN UPDATE DST
WHEN NOT MATCHED INSERT IN DST

表格结构

Source

Column1 Column2 Column3 Column4
A        A       NULL    NULL
B        B       NULL    NULL

Destination

Column1 Column2 COlumn3 Column4 Column5

错误

MERGE语句尝试多次更新或删除同一行。当目标行与多个源行匹配时会发生这种情况。 MERGE语句不能多次更新/删除目标表的同一行。优化ON子句以确保目标行最多匹配一个源行，或使用GROUP BY子句对源行进行分组。

但是当我使用下面的查询时（即仅使用那些具有某些值且不是空值的列，如SRC中的Column3和Column 4）一切正常

MERGE DST
    USING (SELECT * FROM SRC WHERE <Some_Condition>) SRC
    ON SCR.COL1 = DST.COL1 OR (SRC.COL1 IS NULL AND DST.COl1 IS NULL) AND 
    ON SCR.COL2 = DST.COL2 OR (SRC.COL2 IS NULL AND DST.COl2 IS NULL) 
    WHEN MATCHED UPDATE DST
    WHEN NOT MATCHED BY SOURCE THEN UPDATE DST
    WHEN NOT MATCHED INSERT IN DST

编辑：复制方案

SOURCE TABLE

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[tblSource](
    [Column1] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column2] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column3] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column4] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column5] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF

目的地表

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[tblDestination](
    [Column1] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column2] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column3] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column4] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column5] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL,
    [Column6] [varchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF

资料来源

INSERT [dbo].[tblSource] ([Column1], [Column2], [Column3], [Column4], [Column5]) VALUES (N'A', N'A', NULL, NULL, NULL)
INSERT [dbo].[tblSource] ([Column1], [Column2], [Column3], [Column4], [Column5]) VALUES (N'B', N'B', NULL, NULL, NULL)

目的地为空

合并声明

MERGE dbo.tblDestination DST
USING (SELECT * FROM dbo.tblSource) SRC
ON DST.Column1 = SRC.Column1 OR (DST.Column1 IS NULL AND SRC.Column1 IS NULL) AND
DST.Column2 = SRC.Column2 OR (DST.Column2 IS NULL AND SRC.Column2 IS NULL) AND
DST.Column3 = SRC.Column3 OR (DST.Column3 IS NULL AND SRC.Column3 IS NULL) AND
DST.Column4 = SRC.Column4 OR (DST.Column4 IS NULL AND SRC.Column4 IS NULL) AND
DST.Column5 = SRC.Column5 OR (DST.Column5 IS NULL AND SRC.Column5 IS NULL)

WHEN MATCHED THEN
        UPDATE SET COLUMN5 = 'A'
WHEN NOT MATCHED BY SOURCE THEN
        UPDATE SET Column5 = 'B'
WHEN NOT MATCHED THEN
        INSERT (Column1, Column2, Column3, Column4, Column5)
        VALUES (Column1, Column2, Column3, Column4, Column5) ;

运行两次以查看错误。

现在截断目标表

现在是相同的查询，但只有那些有数据的列

MERGE dbo.tblDestination DST
USING (SELECT * FROM dbo.tblSource) SRC
ON DST.Column1 = SRC.Column1 OR (DST.Column1 IS NULL AND SRC.Column1 IS NULL) AND
DST.Column2 = SRC.Column2 OR (DST.Column2 IS NULL AND SRC.Column2 IS NULL) 


WHEN MATCHED THEN
        UPDATE SET COLUMN5 = 'A'
WHEN NOT MATCHED BY SOURCE THEN
        UPDATE SET Column5 = 'B'
WHEN NOT MATCHED THEN
        INSERT (Column1, Column2, Column3, Column4, Column5)
        VALUES (Column1, Column2, Column3, Column4, Column5) ;

这是非常好的工作，你可以运行它多次运行。

Answer 1

这是Operator Precedence的问题。

无论其他列中的值如何，

DST.Column1 = SRC.Column1 OR (DST.Column1 IS NULL AND SRC.Column1 IS NULL) ....都会匹配DST.Column1 = SRC.Column1的所有行。

您需要在OR：ed条件周围添加一些括号来覆盖默认优先级。

MERGE dbo.tblDestination DST
USING (SELECT * FROM dbo.tblSource) SRC
ON (DST.Column1 = SRC.Column1 OR (DST.Column1 IS NULL AND SRC.Column1 IS NULL)) AND
   (DST.Column2 = SRC.Column2 OR (DST.Column2 IS NULL AND SRC.Column2 IS NULL)) AND
   (DST.Column3 = SRC.Column3 OR (DST.Column3 IS NULL AND SRC.Column3 IS NULL)) AND
   (DST.Column4 = SRC.Column4 OR (DST.Column4 IS NULL AND SRC.Column4 IS NULL)) AND
   (DST.Column5 = SRC.Column5 OR (DST.Column5 IS NULL AND SRC.Column5 IS NULL))

WHEN MATCHED THEN
        UPDATE SET COLUMN5 = 'A'
WHEN NOT MATCHED BY SOURCE THEN
        UPDATE SET Column5 = 'B'
WHEN NOT MATCHED THEN
        INSERT (Column1, Column2, Column3, Column4, Column5)
        VALUES (Column1, Column2, Column3, Column4, Column5) ;

列中为空时合并语句错误

1 个答案: