SQL> select * from mhe_tab;

        ID   PARENTID
---------- ----------
         1          0
         2          1
         3          1
         4          2

SQL> select parentid
  2    from mhe_tab
  3  connect by id = prior parentid
  4    start with id = &the_id
  5  /
Enter value for the_id: 4
old   4:   start with id = &the_id
new   4:   start with id = 4

  PARENTID
----------
         2
         1
         0

SQL> /
Enter value for the_id: 2
old   4:   start with id = &the_id
new   4:   start with id = 2

  PARENTID
----------
         1
         0