That what we get when assuming anything. :)
Now lets wait and see who's assumption is correct.

>But I am not referencing X2 and Y2, I am referencing nodes.x and nodes.y.
>If they are calculated fields, you are right, but they are not (if the example SELECT is correct).
>
>>It's not going to work. You cannot reference calculated fields in consequent calculations in the same list. You can use derived table

>>SELECT *, ABS(dt1.x2-dt2.y2) AS dx ;
>>  FROM ( ;
>>select temp1.*,nodes.x as x2, nodes.y as y2,
>>	from UPDNETATR!xydata nodes ;
>>	right outer join temp1 ;
>>	on  nodes.n = temp1.b;
>>	where st_name <> ' ' ;
>>	order by temp1.st_name ;
>>       ) dt1
>>

>>>Yes it is:
>>>BTW the result contains x2 and Y2 :-)
>>>of course if you didn't have X1 in Temp1
>>>

>>>select temp1.*,nodes.x as x2, nodes.y as y2, ABS(nodes.x-nodes.y) AS dx;
>>>	from UPDNETATR!xydata nodes ;
>>>	right outer join temp1 ;
>>>	on  nodes.n = temp1.b;
>>>	where st_name <> ' ' ;
>>>	order by temp1.st_name
>>>