有TA, TB兩表，假設均有三個欄位id, name, remark. 現在需要把TB表的name, remark兩個欄位通過id關聯，更新到TA表的對應欄位。

建表指令碼：

drop table TA;
create table TA
(
id number not null,
name varchar(10) not null,
remark varchar(10) not null
);

drop table TB;
create table TB
(
id number not null,
name varchar(10) not null,
remark varchar(10) not null
);

truncate table TA;
insert into TA values(1, 'Aname1', 'Aremak1');
insert into TA values(2, 'Aname2', 'Aremak2');
commit;

truncate table TB;
insert into TB values(1, 'Bname1', 'Bremak1');
insert into TB values(3, 'Bname3', 'Bremak3');
commit;

select * from TA;
select * from TB;
 

SQLServer/Oracle版本的Update寫法分別如下：

1. SQLServer

update TA set name=b.name, remark=b.remark from TA a inner join TB b on a.id = b.id

或者

update TA set name=b.name, remark=b.remark from TA a, TB b where a.id = b.id

Msg 4104, Level 16, State 1, Line 1
The multi-part identifier "a.name" could not be bound.

2. Oracle

update TA a set(name, remark)=(select b.name, b.remark from TB b where b.id=a.id) 
where exists(select 1 from TB b where b.id=a.id)

注意如果不新增後面的exists語句，TA關聯不到的行name, remark欄位將被更新為NULL值， 如果name, remark欄位不允許為null，則報錯。 這不是我們希望看到的。

--when name, remark is not null, cause error. 
--if allow null, rows in TA not matched will be update to null.
update TA a set(name, remark)=(select b.name, b.remark from TB b where b.id=a.id);
 

可考慮的替代方法：

update TA a set name= nvl((select b.name from TB b where b.id=a.id), a.name);
update TA a set remark= nvl((select b.remark from TB b where b.id=a.id), a.remark);

如果TA.id, TB.id是unique index或primary key

可以使用檢視更新的語法：

ALTER TABLE TA ADD CONSTRAINT TA_PK
  PRIMARY KEY (
  ID
)
 ENABLE
 VALIDATE
;

ALTER TABLE TB ADD CONSTRAINT TB_PK
  PRIMARY KEY (
  ID
)
 ENABLE
 VALIDATE
;

update (select a.name, b.name as newname, 
a.remark, b.remark as newremark from TA a, TB b where a.id=b.id)
set name=newname, remark=newremark;