> > adhoc=# update users set postaladdressid=null where id=50;
> > UPDATE 1
> >
> > adhoc=# select id,postaladdressid from users where postaladdressid=null;
> > id | postaladdressid
> > ----+-----------------
> > (0 rows)
> >
> > Why did it not select record 50?
>
> Because NULL=NULL is not true (it's unknown). Use IS NULL if you want to
> see if something is NULL.
If in postgresql.conf set parameter transform_null_equals=TRUE ????