Select Code to Download

select
 *
...
a_outter_joined.pk2 = b.pk2 (+) and
(a_outter_joined.pk1 = b.pk1 or a_outter_joined.pk1 = null )

select
   *
...
where
   a.pk1 = b.pk1 (+) and
   a.pk2 = b.pk2 (+)