Re: BUG #1677: Bug in select with Union - Mailing list pgsql-bugs

"Julien Vallet" <julien.vallet@density-tech.com> writes:
> The result is "ERROR:  UNION types text and bigint cannot be matched"

This is the identical issue reported here:
http://archives.postgresql.org/pgsql-bugs/2005-02/msg00008.php
See also this thread:
http://archives.postgresql.org/pgsql-general/2005-02/msg00693.php

The short answer is that what you wrote is illegal per the SQL spec
(which doesn't allow NULL to be used in ways where a type can't be
ascribed immediately).  While we'd like to accept it, we have
not figured out a rule that doesn't break the spec in other ways.
For now I'd recommend casting the NULLs explicitly.

            regards, tom lane