MERGE INTO USING用法

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 MATHED THEN [here you can execute some update sql or something else ]
WHEN NOT MATHED THEN [execute something else here ! ] 

MERGE INTO table1 a USING ( select id,name from table2) b ON (a.id=b.id)     
WHEN MATHED THEN update set a.name=b.name
WHEN NOT MATHED THEN insert (id,name) values(‘id‘,‘name‘);