Re: UNION and ORDER BY ... IS NULL ASC

Josh Berkus <josh@agliodbs.com> writes:
>> ERROR:  ORDER BY on a UNION/INTERSECT/EXCEPT result must be on one of 
>> the result columns

> I do believe that this is per the SQL spec; UNIONs may only be sorted on the 
> output columns.

Right.  We extend the SQL spec for ORDER BY on simple selects, but we
have not gotten around to doing so for ORDER BY on set-operation
results.  You can only sort by unadorned output columns.

Patches to improve this are welcome ;-)
        regards, tom lane