What is the best way to fetch Tree/Hierarchical structure data from Oracle

I want to fetch Hierarchical/Tree data something like below from a Table which has following definiton.

Tree Table:
"""""""""""
Id   |ParentId
"""""""""""
Work1|null
Work2|Work1
Work3|Work2
...

Required Query result Data (no need to be tabbed)- If I Pick 'Work1' I should complete Ids which are under its root something like below. If I pick 'Work2' then also I should complete Ids above and below its root.

> Work1 
----开发者_如何学编程------
>   Work2
----------
>     Work3
---------

I used below query but it is giving me duplicate records.

select Id from TreeTable start with Id in ('Work1','Work2') connect by nocycle Parentid=prior Id or Id = prior Parentid

Note: I want to get the data within a SINGLE QUERY (optimized) way

Thanks and Regards, PV.

SELECT  id
FROM    q
START WITH
        id IN ('Work1', 'Work2')
CONNECT BY
        parent = PRIOR id
        AND id NOT IN ('Work1', 'Work2')

This condition:

AND id NOT IN ('Work1', 'Work2')

will cut off the branches already selected with START WITH.