Avoid inserting in oracle [duplicate] - oracle

Question

I need to be able to run an Oracle query which goes to insert a number of rows, but it also checks to see if a primary key exists and if it does, then it skips that insert. Something like:
INSERT ALL
IF NOT EXISTS( SELECT 1 WHERE fo.primary_key='bar' )
(
INSERT INTO
schema.myFoo fo ( primary_key, value1, value2 )
VALUES
('bar','baz','bat')
),
IF NOT EXISTS( SELECT 1 WHERE fo.primary_key='bar1' )
(
INSERT INTO
schema.myFoo fo ( primary_key, value1, value2 )
VALUES
('bar1','baz1','bat1')
)
SELECT * FROM schema.myFoo;
Is this at all possible with Oracle?
Bonus points if you can tell me how to do this in PostgreSQL or MySQL.

Answer 1

Coming late to the party, but...
With oracle 11.2.0.1 there is a semantic hint that can do this: IGNORE_ROW_ON_DUPKEY_INDEX
Example:
insert /*+ IGNORE_ROW_ON_DUPKEY_INDEX(customer_orders,pk_customer_orders) */
into customer_orders
(order_id, customer, product)
values ( 1234, 9876, 'K598')
;
UPDATE: Although this hint works (if you spell it correctly), there are better approaches which don't require Oracle 11R2:
First approach—direct translation of above semantic hint:
begin
insert into customer_orders
(order_id, customer, product)
values ( 1234, 9876, 'K698')
;
commit;
exception
when DUP_VAL_ON_INDEX
then ROLLBACK;
end;
Second aproach—a lot faster than both above hints when there's a lot of contention:
begin
select count (*)
into l_is_matching_row
from customer_orders
where order_id = 1234
;
if (l_is_matching_row = 0)
then
insert into customer_orders
(order_id, customer, product)
values ( 1234, 9876, 'K698')
;
commit;
end if;
exception
when DUP_VAL_ON_INDEX
then ROLLBACK;
end;

Answer 2

The statement is called MERGE. Look it up, I'm too lazy.
Beware, though, that MERGE is not atomic, which could cause the following effect (thanks, Marius):
SESS1:
create table t1 (pk int primary key, i int);
create table t11 (pk int primary key, i int);
insert into t1 values(1, 1);
insert into t11 values(2, 21);
insert into t11 values(3, 31);
commit;
SESS2: insert into t1 values(2, 2);
SESS1:
MERGE INTO t1 d
USING t11 s ON (d.pk = s.pk)
WHEN NOT MATCHED THEN INSERT (d.pk, d.i) VALUES (s.pk, s.i);
SESS2: commit;
SESS1: ORA-00001

Answer 3

We can combine the DUAL and NOT EXISTS to achieve your requirement:
INSERT INTO schema.myFoo (
primary_key, value1, value2
)
SELECT
'bar', 'baz', 'bat'
FROM DUAL
WHERE NOT EXISTS (
SELECT 1
FROM schema.myFoo
WHERE primary_key = 'bar'
);

Answer 4

This only inserts if the item to be inserted is not already present.
Works the same as:
if not exists (...) insert ...
in T-SQL
insert into destination (DESTINATIONABBREV)
select 'xyz' from dual
left outer join destination d on d.destinationabbrev = 'xyz'
where d.destinationid is null;
may not be pretty, but it's handy :)

Answer 5

If you do NOT want to merge in from an other table, but rather insert new data... I came up with this. Is there perhaps a better way to do this?
MERGE INTO TABLE1 a
USING DUAL
ON (a.C1_pk= 6)
WHEN NOT MATCHED THEN
INSERT(C1_pk, C2,C3,C4)
VALUES (6, 1,0,1);

Answer 6

It that code is on the client then you have many trips to the server so to eliminate that.
Insert all the data into a temportary table say T with the same structure as myFoo
Then
insert myFoo
select *
from t
where t.primary_key not in ( select primary_key from myFoo)
This should work on other databases as well - I have done this on Sybase
It is not the best if very few of the new data is to be inserted as you have copied all the data over the wire.

Answer 7

DECLARE
tmp NUMBER(3,1);
BEGIN
SELECT COUNT(content_id) INTO tmp FROM contents WHERE (condition);
if tmp != 0 then
INSERT INTO contents VALUES (...);
else
INSERT INTO contents VALUES (...);
end if;
END;
I used the code above. It is long, but, simple and worked for me. Similar, to Micheal's code.

Answer 8

If your table is "independent" from others (I mean, it will not trigger a cascade delete or will not set any foreign keys relations to null), a nice trick could be to first DELETE the row and then INSERT it again. It could go like this:
DELETE FROM MyTable WHERE prop1 = 'aaa'; //assuming it will select at most one row!
INSERT INTO MyTable (prop1, ...) VALUES ('aaa', ...);
If your are deleting something which does not exist, nothing will happen.

Answer 9

This is an answer to the comment posted by erikkallen:
You don't need a temp table. If you
only have a few rows, (SELECT 1 FROM
dual UNION SELECT 2 FROM dual) will
do. Why would your example give
ORA-0001? Wouldn't merge take the
update lock on the index key and not
continue until Sess1 has either
committed or rolled back? – erikkallen
Well, try it yourself and tell me whether you get the same error or not:
SESS1:
create table t1 (pk int primary key, i int);
create table t11 (pk int primary key, i int);
insert into t1 values(1, 1);
insert into t11 values(2, 21);
insert into t11 values(3, 31);
commit;
SESS2: insert into t1 values(2, 2);
SESS1:
MERGE INTO t1 d
USING t11 s ON (d.pk = s.pk)
WHEN NOT MATCHED THEN INSERT (d.pk, d.i) VALUES (s.pk, s.i);
SESS2: commit;
SESS1: ORA-00001

Answer 10

INSERT INTO schema.myFoo ( primary_key , value1 , value2 )
SELECT 'bar1' AS primary_key ,'baz1' AS value1 ,'bat1' AS value2 FROM DUAL WHERE (SELECT 1 AS value FROM schema.myFoo WHERE LOWER(primary_key) ='bar1' AND ROWNUM=1) is null;