insert if not exists 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

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 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

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