oracle merge into用法

需求，当符合条件1 修改 A表 或 新增 A表 oracle 写法

语法:

merge into 目标表 a
 
using 源表 b
 
on(a.条件字段1=b.条件字段1 and a.条件字段2=b.条件字段2 ……)  
 
when matched then update set a.更新字段=b.字段
 
when  not matched then insert into a(字段1,字段2……)values(值1,值2……)

例子：

MERGE INTO T T1
 
USING (SELECT '1001' AS a, 2 AS b FROM dual)  T2
 
ON ( T1.a=T2.a)
 
WHEN MATCHED THEN
 
UPDATE SET T1.b= T2.b
 
WHEN NOT MATCHED THEN
 
INSERT (a,b) VALUES(T2.a,T2.b);