SQL Server 2008的实用小道具——merger(转：http://database.ctocio.com.cn/18/11525518.shtml)

根据在另一个表中找到的差异在一个表中插入、更新或删除行，可以对两个表进行同步。

　　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

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'

 

 

 

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.*;

 

 

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