SQL99 "with recursive" question

Hello, i think i am to stupid to use the "with recursive" SQL!

I have a table:

create table tree
(
id_tree integer,
parent_id integer
....
);

In PostgreSQL i use the great connectby() function and in Oracle i simple
use

select * from tree
start with id_tree = 0
connect by parent_id=prior id_tree

But how must i use this with "with recursive" function?
Every example i found uses two tables. I have only one!

Please help me! I need this to use my oracle tables with
the same speed in sybase 9.0.
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Thomas Wegner
Cabrio Meter - The Weather Plugin for Trillian
http://trillian.wegner24.de/cabriometer