SQL & PL/SQL

Hello,

i was wondering how to make automatic numbering of primary key without using sequence when "on" insert.

At the moment i am using trigger:

TRIGGER "scott"."do_numbers" BEFORE INSERT ON "scott"."test" 
REFERENCING NEW AS NEW FOR EACH ROW 

declare
 pragma autonomous_transaction;
begin

SELECT
 nvl(MAX(ID),0)+1
 INTO :NEW.ID
  FROM test;
commit;
END;

the above trigger works when i am inserting row by row. But now i tried to insert 300 rows at once. Here insert fails ... i think there should be commit after each insert (thats what i think).

Can someone explain it to me how can this "automatic" numbering can be done when inserting large number or rows from one table to another at once?

thank you!