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