SQLServer 2008 Merge语句的OUTPUT功能

答案：下面介绍一下把Output同2008的新T-SQL语句Merge组合使用的方法： 
新建下面表：
复制代码 代码如下:

CREATE TABLE Book( 
ISBN varchar(20) PRIMARY KEY, 
Price decimal, 
Shelf int) 

CREATE TABLE WeeklyChange( 
ISBN varchar(20) PRIMARY KEY, 
Price decimal, 
Shelf int) 

CREATE TABLE BookHistory( 
Action nvarchar(10), 
NewISBN varchar(20), 
NewPrice decimal, 
NewShelf int, 
OldISBN varchar(20), 
OldPrice decimal, 
OldShelf int, 
ArchivedAt datetime2)

SQL语句为 
复制代码 代码如下:

MERGE Book AS B 
USING WeeklyChange AS WC 
ON B.ISBN = WC.ISBN 
WHEN MATCHED AND (B.Price <> WC.Price OR B.Shelf <> WC.Shelf) THEN 
UPDATE SET B.Price = WC.Price, B.Shelf = WC.Shelf 
WHEN NOT MATCHED THEN 
INSERT VALUES(WC.ISBN, WC.Price, WC.Shelf) 
OUTPUT $action, inserted.*, deleted.*, SYSDATETIME() 
INTO BookHistory; 

结果集为： 

SELECT * FROM BookHistory 
GO 

Action NewISBN NewPrice NewShelf OldISBN OldPrice OldShelf ArchivedAt 
------ ------- -------- -------- ------- -------- -------- --------------------------- 
UPDATE A 101 1 A 100 1 2007-11-25 14:47:23.9907552 
INSERT C 300 3 NULL NULL NULL 2007-11-25 14:47:23.9907552 

这里有Insert和Update两种Output情况。如果只需要其中一种，可以用下面这种方法过滤： 
复制代码 代码如下:

INSERT INTO Book(ISBN, Price, Shelf, ArchivedAt) 
SELECT ISBN, Price, Shelf, GETDATE() FROM 
(MERGE Book AS B 
USING WeeklyChange AS WC 
ON B.ISBN = WC.ISBN AND B.ArchivedAt IS NULL 
WHEN MATCHED AND (B.Price <> WC.Price OR B.Shelf <> WC.Shelf) THEN 
UPDATE SET Price = WC.Price, Shelf = WC.Shelf 
WHEN NOT MATCHED THEN 
INSERT VALUES(WC.ISBN, WC.Price, WC.Shelf, NULL) 
OUTPUT $action, WC.ISBN, Deleted.Price, Deleted.Shelf 
) CHANGES(Action, ISBN, Price, Shelf) 
WHERE Action = 'UPDATE';

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