WITH TMP AS (SELECT   1 AS ID, NULL AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   2 AS ID, 1 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   3 AS ID, 2 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   4 AS ID, 3 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   5 AS ID, 3 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   6 AS ID, 2 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   7 AS ID, 1 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   8 AS ID, NULL AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   9 AS ID, 8 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   10 AS ID, 8 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   11 AS ID, 10 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   12 AS ID, NULL AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   13 AS ID, 12 AS PARENT_ID FROM DUAL 
             UNION 
             SELECT   14 AS ID, NULL AS PARENT_ID FROM DUAL), 
    LVL_BREAKDOWN 
       AS (SELECT   LVL, 
                    ID_PATH, 
                    TO_NUMBER (REGEXP_SUBSTR (ID_PATH, 
                                              '[^/]+', 
                                              1, 
                                              1)) 
                       LEVEL1, 
                    TO_NUMBER (REGEXP_SUBSTR (ID_PATH, 
                                              '[^/]+', 
                                              1, 
                                              2)) 
                       LEVEL2, 
                    TO_NUMBER (REGEXP_SUBSTR (ID_PATH, 
                                              '[^/]+', 
                                              1, 
                                              3)) 
                       LEVEL3, 
                    TO_NUMBER (REGEXP_SUBSTR (ID_PATH, 
                                              '[^/]+', 
                                              1, 
                                              4)) 
                       LEVEL4 
             FROM   (    SELECT   LEVEL AS LVL, 
                                  SYS_CONNECT_BY_PATH (ID, '/') ID_PATH 
                           FROM   TMP 
                     START WITH   PARENT_ID IS NULL 
                     CONNECT BY   PRIOR ID = PARENT_ID)) 
SELECT   LB1.* 
  FROM   LVL_BREAKDOWN LB1 
 WHERE   lvl = 4 
UNION 
SELECT   LB1.* 
  FROM   LVL_BREAKDOWN LB1 
 WHERE   lvl = 3 
         AND NOT EXISTS 
               (SELECT   'x' 
                  FROM   LVL_BREAKDOWN LB2 
                 WHERE       LB1.LEVEL1 = LB2.LEVEL1 
                         AND LB1.LEVEL2 = LB2.LEVEL2 
                         AND LB1.LEVEL3 = LB2.LEVEL3 
                         AND lvl = 4) 
UNION 
SELECT   LB1.* 
  FROM   LVL_BREAKDOWN LB1 
 WHERE   lvl = 2 
         AND NOT EXISTS 
               (SELECT   'x' 
                  FROM   LVL_BREAKDOWN LB2 
                 WHERE       LB1.LEVEL1 = LB2.LEVEL1 
                         AND LB1.LEVEL2 = LB2.LEVEL2 
                         AND lvl = 3) 
UNION 
SELECT   LB1.* 
  FROM   LVL_BREAKDOWN LB1 
 WHERE   lvl = 1 
         AND NOT EXISTS (SELECT   'x' 
                           FROM   LVL_BREAKDOWN LB2 
                          WHERE   LB1.LEVEL1 = LB2.LEVEL1 AND lvl = 2) 
ORDER BY   3, 4 ASC