OSEK的设计哲学与架构

功能描述

通过MERGE INTO语句，将目标表和源表中数据针对关联条件进行匹配，若关联条件匹配时对目标表进行UPDATE，无法匹配时对目标表执行INSERT。
此语法可以很方便地用来合并执行UPDATE和INSERT，避免多次执行。

进行MERGE INTO操作的用户需要同时拥有目标表的UPDATE和INSERT权限，以及源表的SELECT权限。

示例:

--测试表1
DROP TABLE test;
create table test
(
id int NOT NULL,
name varchar2(50) DEFAULT NULL ,
CONSTRAINT "pk_id2" PRIMARY KEY (id)
) ;
insert into test
select '1','one' FROM dual
 union all 
select '2','two' FROM dual
 union all 
select '3','three' FROM dual

SELECT * FROM test;
ID	NAME
1	one
2	two
3	three

--测试表2
drop TABLE test2;
create table test2 
(
id int NOT NULL,
name varchar2(50) DEFAULT NULL ,
CONSTRAINT "pk_id" PRIMARY KEY (id)
) ;

insert into test2
select '1','oneone' FROM dual
 union all 
select '4','four' FROM dual


SELECT * FROM test2;
1	oneone
4	four

--merge into 语法

merge into test t1
using test2 t2
on (t1.id = t2.id)
WHEN MATCHED THEN  
	update set t1.name = t2.name 
WHEN NOT MATCHED THEN  
	insert values (t2.id, t2.name);

Updated ROWS 2

SELECT * FROM  test;
ID	NAME
1	oneone
2	two
3	three
4	four