<christiangda@cantv.net> writes:
> <DIV><FONT face=3DArial size=3D2>I have PostgreSQL v7.02 in RedHat 6.2;</FO=
NT> </DIV>
> <DIV><FONT face=3DArial size=3D2></FONT> </DIV>
> <DIV><FONT face=3DArial size=3D2>I have problem with is Query:</FONT></DIV>
> <DIV><FONT face=3DArial size=3D2>select name, 'user' as class from smuser u=
> nion=20
> select name, 'group' as class from smgroup order by class;</FONT></DIV>
> <DIV><FONT face=3DArial size=3D2></FONT> </DIV>
Please turn off HTML mail :-(
The problem is with the nonspecific-type literals; 7.0 won't resolve
those to a particular datatype by itself, so it doesn't know how to sort
them. Try
select name, 'user'::text as class from smuser
union
select name, 'group'::text as class from smgroup
order by class;
regards, tom lane