SQL> ED
Wrote file afiedt.buf

  1  select
  2  table_name from
  3  (select
  4  table_name,max(level) maxlevel
  5  from
  6  (select t1.table_name table_name, t2.table_name pk_table_name from
  7  user_constraints t1,
  8  user_constraints t2,
  9  user_tables t3,
 10  user_tables t4
 11  where
 12  t1.constraint_type='R' and
 13  t1.status='ENABLED'
 14  t1.r_constraint_name=t2.constraint_name and
 15  t1.table_name=t3.table_name and t2.table_name=t4.table_name)
 16  connect by prior table_name=pk_table_name
 17  group by table_name
 18  union
 19  (select table_name, 0 maxlevel from user_tables minus select table_name,0
 20  from user_constraints where constraint_type='R' and status='ENABLED')
 21  )
 22* order by maxlevel desc
 23  /
t1.r_constraint_name=t2.constraint_name and
*
ERROR at line 14:
ORA-00907: missing right parenthesis


SQL> 

SELECT table_name 
FROM   (SELECT table_name, 
               Max(LEVEL) maxlevel 
        FROM   (SELECT t1.table_name table_name, 
                       t2.table_name pk_table_name 
                FROM   user_constraints t1, 
                       user_constraints t2, 
                       user_tables t3, 
                       user_tables t4 
                WHERE  t1.constraint_type = 'R' 
                       AND t1.status = 'ENABLED' 
                       AND t1.r_constraint_name = t2.constraint_name 
                       AND t1.table_name = t3.table_name 
                       AND t2.table_name = t4.table_name) 
        CONNECT BY PRIOR table_name = pk_table_name 
        GROUP  BY table_name 
        UNION 
        (SELECT table_name, 
                0 maxlevel 
         FROM   user_tables 
         MINUS 
         SELECT table_name, 
                0 
         FROM   user_constraints 
         WHERE  constraint_type = 'R' 
                AND status = 'ENABLED')) 
ORDER  BY maxlevel DESC;