ORACLE两表关联更新三种方式

不多说了，我们来做实验吧。

准备工作

创建如下表数据

drop table demo_t1;
drop table demo_t2;
CREATE TABLE DEMO_T1 
(
  FNAME VARCHAR2(20) 
, FMONEY VARCHAR2(20) 
);
ALTER TABLE demo_t1 ADD PRIMARY KEY(FNAME);
insert into demo_t1 (fname,fmoney) values('A','20');
insert into demo_t1 (fname,fmoney) values('B','30');
CREATE TABLE DEMO_T2
(
  FNAME VARCHAR2(20) 
, FMONEY VARCHAR2(20) 
);
ALTER TABLE demo_t2 ADD PRIMARY KEY(FNAME);
insert into demo_t2 (fname,fmoney) values('C','10');
insert into demo_t2 (fname,fmoney) values('D','20');
insert into demo_t2 (fname,fmoney) values('A','100');

 现需求：参照T2表，修改T1表，修改条件为两表的fname列内容一致。

方式1：update

UPDATE DEMO_T1 t1
SET T1.FMONEY = (select T2.FMONEY from DEMO_T2 T2 where T2.FNAME = T1.FNAME)
WHERE EXISTS(SELECT 1 FROM DEMO_T2 T2 WHERE T2.FNAME = T1.FNAME);

如果同时更新多个字段可以参照以下语法：

UPDATE DEMO_T1 t1
SET (字段一,字段二,...) = (select 字段一,字段二,... from DEMO_T2 T2 where T2.FNAME = T1.FNAME)
WHERE EXISTS(SELECT 1 FROM DEMO_T2 T2 WHERE T2.FNAME = T1.FNAME);

方式2：内联视图更新

注意：需要取数据的表，该字段必是主键或者有唯一约束

UPDATE (
select t1.fmoney  fmoney1,t2.fmoney  fmoney2 from demo_t1 t1,demo_t2 t2 where t1.fname = t2.fname
)t
set fmoney1 =fmoney2;

方式3：merge更新

merge into demo_t1 t1
using (select t2.fname,t2.fmoney from demo_t2 t2) t
on (t.fname = t1.fname)
when matched then 
  update  set t1.fmoney = t.fmoney;