If understand you correctly, the tables are linked by 'dcode' field. In this case try

SELECT iif(!empty(localdesc),localdesc,DESCRIPTIO),PADR(dcode,15) AS dcode1 ;
	FROM (gcProcDBF) ;
	where screenoption=[RADIOLOGY] ;
	UNION ALL ;
	SELECT procalias, PADR(dcode,15) AS dcode1 ;
	FROM (gcPAlias) ;
	WHERE dcode IN ( SELECT dcode FROM (gcProcDBF) ;
			where screenoption=[RADIOLOGY] );
	ORDER BY 1 ;
	INTO ARRAY RADPROCS

>I have a table called proc.dbf and child table called palias.dbf
>
>I'm trying to return all records for a lookup from the proc.dbf and palias (dcode) is what they are common on. The query below will do that. BUT...always a but.. I'm filtering the query on the proc.dbf if the screen option = RADIOLOGY. This works on the top sql, but since the child table doesn't have that field, it returns all records from the palias table. So my question is how can I re-write this query to also apply the filter to the palias?
>
>Thanks for any help:
>
>

>gcProcDBF=[..\proc.dbf]
>gcPalias=[..\palias]
>SELECT iif(!empty(localdesc),localdesc,DESCRIPTIO),PADR(dcode,15) AS dcode1 ;
>	FROM &gcProcDBF ;
>	where screenoption=[RADIOLOGY] ;
>	UNION ALL ;
>	SELECT procalias, PADR(dcode,15) AS dcode1 ;
>	FROM &gcPAlias ;
>	ORDER BY 1 ;
>	INTO ARRAY RADPROCS
>