使用 MERGE 在单个语句中对表执行 INSERT 和 UPDATE 操作

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USE AdventureWorks2012;
GO
CREATE PROCEDURE dbo.InsertUnitMeasure
    @UnitMeasureCode nchar(3),@Name nvarchar(25)
AS 
BEGIN
    SET NOCOUNT ON;
-- Update the row if it exists.    
    UPDATE Production.UnitMeasure
	SET Name = @Name
	WHERE UnitMeasureCode = @UnitMeasureCode
-- Insert the row if the UPDATE statement failed.	
	IF (@@ROWCOUNT = 0 )
	BEGIN
	    INSERT INTO Production.UnitMeasure (UnitMeasureCode,Name)
	    VALUES (@UnitMeasureCode,@Name)
	END
END;
GO
-- Test the procedure and return the results.
EXEC InsertUnitMeasure @UnitMeasureCode = 'ABC',@Name = 'Test Value';
SELECT UnitMeasureCode,Name FROM Production.UnitMeasure
WHERE UnitMeasureCode = 'ABC';
GO

-- Rewrite the procedure to perform the same operations using the MERGE statement.
-- Create a temporary table to hold the updated or inserted values from the OUTPUT clause.
CREATE TABLE #MyTempTable
    (ExistingCode nchar(3),ExistingName nvarchar(50),ExistingDate datetime,ActionTaken nvarchar(10),NewCode nchar(3),NewName nvarchar(50),NewDate datetime
    );
GO
ALTER PROCEDURE dbo.InsertUnitMeasure
    @UnitMeasureCode nchar(3),@Name nvarchar(25)
AS 
BEGIN
    SET NOCOUNT ON;

    MERGE Production.UnitMeasure AS target
    USING (SELECT @UnitMeasureCode,@Name) AS source (UnitMeasureCode,Name)
    ON (target.UnitMeasureCode = source.UnitMeasureCode)
    WHEN MATCHED THEN 
        UPDATE SET Name = source.Name
	WHEN NOT MATCHED THEN	
	    INSERT (UnitMeasureCode,Name)
	    VALUES (source.UnitMeasureCode,source.Name)
	    OUTPUT deleted.*,$action,inserted.* INTO #MyTempTable;
END;
GO
-- Test the procedure and return the results.
EXEC InsertUnitMeasure @UnitMeasureCode = 'ABC',@Name = 'New Test Value';
EXEC InsertUnitMeasure @UnitMeasureCode = 'XYZ',@Name = 'Test Value';
EXEC InsertUnitMeasure @UnitMeasureCode = 'ABC',@Name = 'Another Test Value';

SELECT * FROM #MyTempTable;
-- Cleanup 
DELETE FROM Production.UnitMeasure WHERE UnitMeasureCode IN ('ABC','XYZ');
DROP TABLE #MyTempTable;
GO

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