The CONNECT BY operator can be used to define hierarchical conditions. For more details on the usage of this operator, refer to the CONNECT BY clause in the SELECT statement section.
PRIOR last_name PARENT_NAME,
CONNECT_BY_ROOT last_name ROOT_NAME,
SYS_CONNECT_BY_PATH(last_name, '/') "PATH"
CONNECT BY PRIOR employee_id = manager_id
START WITH last_name = 'Clark';