SQL & PL/SQL

Hi,

I have data something like below

SKU:
--------
ITEM LOC PARENT_ITEM PARENT_LOC
------------------------------------------------------------------------------------------------------------
NULL NULL A 001
A 001 NULL NULL
A 001 NULL NULL
NULL NULL D 002
D 002 NULL NULL
D 002 NULL NULL

And I need output like this

ITEM LOC PARENT_ITEM PARENT_LOC
------------------------------------------------------------------------------------------------------------
NULL NULL A 001
B 001 A 001
C 001 A 001
NULL NULL D 002
E 002 D 002
F 002 D 002


And I tried it with connect by prior.

Select CONNECT_BY_ROOT as item,loc,parent_item,parent_loc FROM
sku
start with parent_item is null and parent_loc is null
connect by prior parent_item = item and parent_loc = loc

But I am getting only parent record not others.
ITEM LOC PARENT_ITEM PARENT_LOC
------------------------------------------------------------------------------------------------------------
A NULL A 001
D NULL D 002


I should apply CONNECT_BY_ROOT and connect by PRIOR on set (like item at loc).
Please help..

Thanks...