ORACLE 10 g的 merge into 用法

在Oracle 10g之前，merge语句支持匹配更新和不匹配插入2种简单的用法，在10g中Oracle对merge语句做了增强，增加了条件选项和DELETE操作。下面我通过一个demo来简单介绍一下10g中merge的增强和10g前merge的用法。

参考Oracle 的SQL Reference 下面我在一下环境中做一个测试看看

创建表subs  和 acct

create table subs(
       msid     number(9),
       ms_type  char(1),
       areacode number(3)
);

create table acct(
       msid       number(9),
       bill_month number(6),
       areacode   number(3),
       fee        number(8,2) default 0.00
);

插入数据

insert into subs values(905310001,0,531);
insert into subs values(905320001,1,532);
insert into subs values(905330001,2,533);
commit

语法

--  语法
merge [into [schema .] table [t_alias]
 　using [schema .] { table | view | subquery } [t_alias]
　　  on ( condition )
　　     when matched then
            merge_update_clause
　　     when not matched then
            merge_insert_clause;

测试

---  matched：更新    not matched：插入  两者可以同步执行也可以只要一个条件
merge into acct a
   using subs b
      on (a.msid = b.msid)
         when matched then
            update set a.areacode = 22
         when not matched then
            insert (msid, bill_month, areacode) values (b.msid, '200702', b.areacode);
commit

增强条件查询操作

merge into acct a
   using subs b
      on (a.msid = b.msid)
         when matched then
            update set a.areacode = 22 where b.ms_type = 0
         when not matched then
            insert (msid, bill_month, areacode) values (b.msid, '200702', b.areacode) where b.ms_type = 0;
commit

增强删除操作

merge into acct a
   using subs b
      on (a.msid = b.msid)
         when matched then
            update set a.areacode = 22
            delete where (b.ms_type != 0);
commit