merge into

--Merge 简单应用：
--1、以另一个表作为源表：
---创建源表
Create Table OriginTable(id Int,caption VarChar(50))
---创建操作表
Create Table TargetTable(id Int,caption VarChar(50))
--插入测试数据
Insert Into dbo.OriginTable(id,caption)VALUES(1,'测试1')
Insert Into dbo.OriginTable(id,caption)VALUES(2,'测试2')
Insert Into dbo.OriginTable(id,caption)VALUES(3,'测试3')
Insert Into dbo.OriginTable(id,caption)VALUES(4,'测试4')
Insert Into dbo.TargetTable(id,caption)VALUES(1,'目标表匹配到了源表则update1')
Insert Into dbo.TargetTable(id,caption)VALUES(3,'目标表匹配到了源表则update2')
Insert Into dbo.TargetTable(id,caption)VALUES(5,'源表里不存在则delete')
Insert Into dbo.TargetTable(id,caption)VALUES(8,'源表里不存在则delete')
Select * from OriginTable
Select * from TargetTable
​
MERGE INTO TargetTable  as T
USING  OriginTable as S 
ON T.id=S.id
WHEN MATCHED --当上面on后的T.id=S.id时，则更新，也可以加上自定义的限制条件 MATCHED AND S.id=2
Then UpDate set T.caption=S.caption
When Not Matched --目标中没有的id ，在源表中有则插入
Then Insert Values(S.id,S.caption)
When Not Matched By SOURCE --目标表中存在源表中不存在则删除
Then Delete;--Merge的最后结尾必须是以分号结束的，不能忘了分号 谨记:语法严格要求关键字之间只能有一个英文空格,不能有多余的空格