Oracle Equivalent to MySQL INSERT IGNORE?

Question

I need to update a query so that it checks that a duplicate entry does not exist before insertion. In MySQL I can just use INSERT IGNORE so that if a duplicate record is fo

Answer 1

Another variant

Insert into my_table (student_id, group_id)
select distinct p.studentid, g.groupid 
from person p, group g
where NOT EXISTS (select 1
                 from my_table a
                 where a.student_id = p.studentid
                 and a.group_id = g.groupid)

or you could do

Insert into my_table (student_id, group_id)
select distinct p.studentid, g.groupid 
from person p, group g
MINUS
select student_id, group_id
from my_table 

Answer 2

Check out the MERGE statement. This should do what you want - it's the WHEN NOT MATCHED clause that will do this.

Do to Oracle's lack of support for a true VALUES() clause the syntax for a single record with fixed values is pretty clumsy though:

MERGE INTO your_table yt
USING (
   SELECT 42 as the_pk_value, 
          'some_value' as some_column
   FROM dual
) t on (yt.pk = t.the_pke_value) 
WHEN NOT MATCHED THEN 
   INSERT (pk, the_column)
   VALUES (t.the_pk_value, t.some_column);

A different approach (if you are e.g. doing bulk loading from a different table) is to use the "Error logging" facility of Oracle. The statement would look like this:

 INSERT INTO your_table (col1, col2, col3)
 SELECT c1, c2, c3
 FROM staging_table
 LOG ERRORS INTO errlog ('some comment') REJECT LIMIT UNLIMITED;

Afterwards all rows that would have thrown an error are available in the table errlog. You need to create that errlog table (or whatever name you choose) manually before running the insert using DBMS_ERRLOG.CREATE_ERROR_LOG.

See the manual for details