You'll want to generate a "sequence", setting an initial number and an increment.

create sequence seq_name 
   start with 1
   increment by 1
   maxvalue 999999
   nocycle
   cache 20;
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then you'll do something similar to this:

INSERT INTO table_name 
  ( id_no, col1, col2 )
values 
  ( seq_name.NEXTVAL, '$col1', '$col2' )
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if you have few inserts and want to not have skipped sequence numbers, then avoid using a cache, it tends to cause "gaps" (at least in our environment)

good luck!

PS: wait for the insert to get the nextval, then display it post-insert. not before, or you'll get into trouble with non-uniqueness, which is what sequences are made to avoid :-)