Oracle存在则更新，不存在则插入应用

MERGE INTO mn a
USING (select count(*) co from mn where mn.ID=4) b
ON (b.co<>0)--这里使用了count和<>，注意下，想下为什么！
WHEN MATCHED THEN
UPDATE
SET a.NAME = 'E'
where a.ID=4
WHEN NOT MATCHED THEN
INSERT
VALUES (4, 'E');

--测试数据
create table table1(id varchar2(100),name varchar2(1000),address varchar2(1000));
insert into table1(id,name,address)values('01001','影子','河北') ;
commit;

--插入
merge into table1 t1
using (select '01002' id,'影子' name,'河北' address from dual) t2
on (t1.id = t2.id)
when matched then
update set t1.name = t2.name, t1.address = t2.address
when not matched then
insert values (t2.id, t2.name,t2.address);
commit;

--查询结果
select * from table1
01001    影子    河北
01002    影子2    辽宁

--更新
merge into table1 t1
using (select '01001' id,'不是影子' name,'山西' address from dual) t2
on (t1.id = t2.id)
when matched then
update set t1.name = t2.name, t1.address = t2.address
when not matched then
insert values (t2.id, t2.name,t2.address);
commit;

--查询结果
select * from table1

01001    不是影子    山西
01002    影子2    辽宁

--删除测试数据
drop table table1;