my $SQL_query;
   
   $SQL_query = qq {SELECT A.DISPLAY_ORDER, A.NAME 
PARENT_NAME, B.NAME CHILD_NAME
FROM CATEGORY A, CATEGORY B 
WHERE B.ID_PARENT_CATEGORY(+) = A.ID_CATEGORY 
AND A.DISPLAY_ORDER != -1 ORDER BY DISPLAY_ORDER};

##</code><code>##

SELECT A.DISPLAY_ORDER, A.NAME PARENT_NAME,  B.NAME CHILD_NAME 
FROM CATEGORY A
LEFT OUTER JOIN  CATEGORY B 
ON B.ID_PARENT_CATEGORY = A.ID_CATEGORY