>> The problem appears to be in the sorting of nulls, which is used by
>> UNION ALL:
>> test=> select null order by 1;
>> ERROR: type id lookup of 0 failed
>
>Hmm. And I've got trouble with the following when I assigned the type
>"UNKNOWNOID" to the null fields:
I think this is ok. Since the first select has to define the datatype, I think a forced
typecasting (like NULL::varchar) is perfectly OK in the above case.
Andreas