MERGE table, do nothing when matched
Solution 1
For your case, no need to use the part:
WHEN MATCHED THEN UPDATE ...
( using WHEN MATCHED THEN UPDATE SET a.id = a.id
is accepted(Oracle doesn't hurl) but has no impact, so, such a usage is redundant, because you don't want to change anything for the matching case. )
If you wanted to change, then add
WHEN MATCHED THEN UPDATE SET a.id = b.id
before
WHEN NOT MATCHED THEN INSERT...
( e.g.Oracle supports
WHEN MATCHED THEN UPDATE
syntax. Refer the Demo below )
Go on with the following for the current case :
SQL> CREATE TABLE domains(
id INT,
name VARCHAR2(50),
code VARCHAR2(50),
description VARCHAR2(50)
);
SQL> INSERT INTO domains VALUES(1,'Domain A','D.A.','This is Domain A');
SQL> MERGE INTO domains A USING
(SELECT 2 id, 'Domain A' name, 'D.A.' code, 'This is Domain A' description
FROM domains) b
ON ( a.name = b.name )
WHEN NOT MATCHED THEN INSERT( a.id, a.name, a.code, a.description )
VALUES( b.id, b.name, b.code, b.description );
SQL> SELECT * FROM domains;
ID NAME CODE DESCRIPTION
-- -------- ----- ----------------
1 Domain A D.A. This is Domain A
SQL> DELETE domains;
SQL> INSERT INTO domains VALUES(1,'Domain A','D.A.','This is Domain A');
-- we're deleting and inserting the same row again
SQL> MERGE INTO domains A USING
(SELECT 2 id, 'Domain B' name, 'D.B.' code, 'This is Domain B' description
FROM domains) b
ON ( a.name = b.name )
WHEN NOT MATCHED THEN INSERT( a.id, a.name, a.code, a.description )
VALUES( b.id, b.name, b.code, b.description );
SQL> SELECT * FROM domains;
ID NAME CODE DESCRIPTION
-- -------- ----- ----------------
1 Domain A D.A. This is Domain A
2 Domain B D.B. This is Domain B
Solution 2
Oracle SQL syntax supports not having any when matched then update
clause.
drop table ft purge;
create table ft (c1 number, c2 varchar2(10));
drop table ld purge;
create table ld (c1 number, c2 varchar2(10));
insert into ft values (1,'a');
insert into ld values (1,'b');
insert into ld values (2,'c');
commit;
merge into ft
using ld
on (ft.c1 = ld.c1)
when not matched then
insert (c1,c2) values (ld.c1,ld.c2);
select * from ft;
C1 C2
--- ---
1 a
2 c
2 rows selected.
user2102665
Updated on October 08, 2021Comments
-
user2102665 over 2 years
I have a table
DOMAINS
in 2 different schemas with columnsID
,NAME
,CODE
,DESCRIPTION
.For any
NAME
exist in new schema, it should use existingID
without any merge; for those newNAME
records, it should insert withID
from old schema.MERGE INTO DOMAINS A USING (SELECT ID,NAME,CODE,DESCRIPTION FROM <Old Schema 6.1>.DOMAINS@DB_MIG_61_TO_74) B ON(A.NAME = B.NAME) WHEN MATCHED **<do nothing>** WHEN NOT MATCHED THEN INSERT(A.ID,A.NAME,A.CODE,A.DESCRIPTION) VALUES(B.ID,B.NAME,B.CODE,B.DESCRIPTION);
How can i intepret the portion of
do nothing
in above query? -
Shannon Fallon over 4 yearsThis works better than the chosen solution when you have a column that shows when the row was last updated that you don't want to change when there's a match.
-
Barbaros Özhan over 4 yearsNo,
when matched then update
is supported