Three methods of Oracle two table Association update

Not much said , Let's do the experiment .

preparation

Create the following table data

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');

  Current demand ： reference T2 surface , modify T1 surface , The modification condition is two tables fname Columns are consistent .

The way 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);

If you update multiple fields at the same time, you can refer to the following syntax ：

UPDATE DEMO_T1 t1
SET ( Field one , Field 2 ,...) = (select  Field one , Field 2 ,... from DEMO_T2 T2 where T2.FNAME = T1.FNAME)
WHERE EXISTS(SELECT 1 FROM DEMO_T2 T2 WHERE T2.FNAME = T1.FNAME);

 

The way 2： Inline view update

Be careful ： Tables requiring data retrieval , This field must be a primary key or have a unique constraint

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

The way 3：merge to update

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;