MERGE INTO：存在就更新不存在就新增——oracle

MERGE INTO [your table-name] [rename your table here]
 
USING ( [write your query here] )[rename your query-sql and using just like a table]
 
ON ([conditional expression here] AND [...]...)
 
WHEN MATCHED THEN [here you can execute some update sql or something else ]
 
WHEN NOT MATCHED THEN [execute something else here ! ]

作用:判断Ｂ表和Ａ表是否满足ON中条件，如果满足则执行满足后面的update SQL，如果不满足，则执行不满足后面的insert SQL。

例子：

使用情况，例如：如果数据库中存在数据就update，如果不存在就insert。

MERGE INTO  TEST T1
 
USING (SELECT '' as ID, 'newtest2' as NAME FROM dual) T2 on (T1.ID=T2.ID)
 
WHEN MATCHED THEN UPDATE SET T1.NAME=T2.NAME
 
WHEN NOT MATCHED THEN  INSERT (T1.ID, T1.NAME) VALUES (T2.ID, T2.NAME );