Merge的山寨版“联机帮助”

IF NOT OBJECT_ID('Demo_AllProducts') IS NULL 
DROP TABLE Demo_AllProducts
GO 

CREATE TABLE Demo_AllProducts
(
    PKID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
    DName NVARCHAR(20) NULL,
    DCode NVARCHAR(20) NULL,
    DDate DATETIME NULL
)
GO  

INSERT INTO Demo_AllProducts
(DName,DCode,DDate)
VALUES
('DemoA','AAA',GETDATE()),
('DemoB','BBB',GETDATE()),
('DemoC','CCC',GETDATE()),
('DemoD','DDD',GETDATE()),
('DemoE','EEE',GETDATE())

SELECT * FROM demo_allproducts

IF NOT OBJECT_ID('Demo_Shop1_product') IS NULL 
DROP TABLE Demo_Shop1_product

CREATE TABLE Demo_Shop1_product
(
    PKID INT NOT NULL IDENTITY(1,1) PRIMARY KEY,
    DName NVARCHAR(20) NULL,
    DCode NVARCHAR(20) NULL,
    DDate DATETIME NULL    
)
GO 

INSERT INTO Demo_Shop1_product
VALUES
('DemoA','AAA',GETDATE()),
('DemoB','CCC',GETDATE()),
('DemoF','FFF',GETDATE())

SELECT * FROM Demo_Shop1_product dsp

--确定目标表
MERGE INTO Demo_AllProducts p 
--查找编码相同的产品
USING Demo_Shop1_product s ON p.DCode=s.DCode
--如果编码相同，名称不同，更新目标表【Demo_AllProducts】名称
WHEN matched AND p.DName<>s.DName THEN UPDATE SET p.DName =s.DName
--如果目标表不存在则插入
WHEN NOT matched BY TARGET THEN INSERT(dname,dcode,ddate) VALUES(s.DName,s.DCode,s.DDate)
--如果目标表数据，子表不存在，删除目标表记录
WHEN NOT matched BY source THEN DELETE ;

土豆的 merge 帮助文档，比联机帮助牛b，哈哈