SQLServer2008的实用小道具 merger使用介绍

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SQLServer2008的实用小道具 merger使用介绍

A. 使用 MERGE 在单个语句中对表执行 UPDATE 和 DELETE 操作
　　下面的示例使用 MERGE 根据 SalesOrderDetail 表中已处理的订单，每天更新 AdventureWorks 示例数据库中的 ProductInventory 表。通过减去每天对 SalesOrderDetail 表中的每种产品所下的订单数，更新 ProductInventory 表的 Quantity 列。如果某种产品的订单数导致该产品的库存量下降到 0 或更少，则会从 ProductInventory 表中删除该产品对应的行。
　　B. 借助派生的源表，使用 MERGE 对目标表执行 UPDATE 和 INSERT 操作
　　下面的示例使用 MERGE 以更新或插入行的方式来修改 SalesReason 表。当源表中的 NewName 值与目标表 (SalesReason) 的 Name 列中的值匹配时，就会更新此目标表中的 ReasonType 列。当 NewName 的值不匹配时，就会将源行插入到目标表中。此源表是一个派生表，它使用 Transact-SQL 行构造函数功能指定源表的多个行。有关在派生表中使用行构造函数的详细信息，请参阅 FROM (Transact-SQL)。

　　C. 将 MERGE 语句的执行结果插入到另一个表中
　　下例捕获从 MERGE 语句的 OUTPUT 子句返回的数据，并将该数据插入另一个表。MERGE 语句根据在 SalesOrderDetail 表中处理的订单，更新 ProductInventory 表的 Quantity 列。本示例捕获已更新的行，并将这些行插入用于跟踪库存变化的另一个表中

复制代码代码如下:

	
	USE AdventureWorks;

	GO

	IF OBJECT_ID (N'Production.usp_UpdateInventory', N'P')

	IS NOT NULL DROP PROCEDURE Production.usp_UpdateInventory;

	GO

	CREATE PROCEDURE Production.usp_UpdateInventory

	@OrderDate datetime

	AS

	MERGE Production.ProductInventory AS target

	USING (SELECT ProductID, SUM(OrderQty) FROM Sales.SalesOrderDetail AS sod

	JOIN Sales.SalesOrderHeader AS soh

	ON sod.SalesOrderID = soh.SalesOrderID

	AND soh.OrderDate = @OrderDate

	GROUP BY ProductID) AS source (ProductID, OrderQty)

	ON (target.ProductID = source.ProductID)

	WHEN MATCHED AND target.Quantity - source.OrderQty <= 0

	THEN DELETE

	WHEN MATCHED

	THEN UPDATE SET target.Quantity = target.Quantity - source.OrderQty,

	target.ModifiedDate = GETDATE()

	OUTPUT $action, Inserted.ProductID, Inserted.Quantity, Inserted.ModifiedDate, Deleted.ProductID,

	Deleted.Quantity, Deleted.ModifiedDate;

	GO

	EXECUTE Production.usp_UpdateInventory '20030501'

复制代码代码如下:

	
	USE AdventureWorks;

	GO

	MERGE INTO Sales.SalesReason AS Target

	USING (VALUES ('Recommendation','Other'), ('Review', 'Marketing'), ('Internet', 'Promotion'))

	AS Source (NewName, NewReasonType)

	ON Target.Name = Source.NewName

	WHEN MATCHED THEN

	UPDATE SET ReasonType = Source.NewReasonType

	WHEN NOT MATCHED BY TARGET THEN

	INSERT (Name, ReasonType) VALUES (NewName, NewReasonType)

	OUTPUT $action, inserted.*, deleted.*;

复制代码代码如下:

	
	USE AdventureWorks;

	GO

	MERGE INTO Sales.SalesReason AS Target

	USING (VALUES ('Recommendation','Other'), ('Review', 'Marketing'), ('Internet', 'Promotion'))

	AS Source (NewName, NewReasonType)

	ON Target.Name = Source.NewName

	WHEN MATCHED THEN

	UPDATE SET ReasonType = Source.NewReasonType

	WHEN NOT MATCHED BY TARGET THEN

	INSERT (Name, ReasonType) VALUES (NewName, NewReasonType)

	OUTPUT $action, inserted.*, deleted.*;

复制代码代码如下:

	
	USE AdventureWorks;

	GO

	CREATE TABLE Production.UpdatedInventory

	(ProductID INT NOT NULL, LocationID int, NewQty int, PreviousQty int,

	CONSTRAINT PK_Inventory PRIMARY KEY CLUSTERED (ProductID, LocationID));

	GO

	INSERT INTO Production.UpdatedInventory

	SELECT ProductID, LocationID, NewQty, PreviousQty

	FROM

	( MERGE Production.ProductInventory AS pi

	USING (SELECT ProductID, SUM(OrderQty)

	FROM Sales.SalesOrderDetail AS sod

	JOIN Sales.SalesOrderHeader AS soh

	ON sod.SalesOrderID = soh.SalesOrderID

	AND soh.OrderDate BETWEEN '20030701' AND '20030731'

	GROUP BY ProductID) AS src (ProductID, OrderQty)

	ON pi.ProductID = src.ProductID

	WHEN MATCHED AND pi.Quantity - src.OrderQty >= 0

	THEN UPDATE SET pi.Quantity = pi.Quantity - src.OrderQty

	WHEN MATCHED AND pi.Quantity - src.OrderQty <= 0

	THEN DELETE

	OUTPUT $action, Inserted.ProductID, Inserted.LocationID, Inserted.Quantity AS NewQty, Deleted.Quantity AS PreviousQty)

	AS Changes (Action, ProductID, LocationID, NewQty, PreviousQty) WHERE Action = 'UPDATE';

	GO

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