A path through a tree

Hi,

OK, I have a feeling that this not something that can be done with SQL but I
may as well give it a shot.

Say you have a table with the following columns:

id int4 NOT NULL UNIQUE
parent int4
value varchar(8)

and each entry represents a node in a tree. So the top most node will have
no parent, and the next nodes will have the 1st node's id as their parent
etc etc etc.

If I have a leaf node, is there a SELECT statement that will give me all the
parent ids on the way to the root? (See diagram below for a different
[probably not better] description).

The tree can be of arbitrary depth.

where i = id and p = parent

i = 1
p = NULL
|
|
+-----+-----+
| |
i = 2 i = 3
p = 1 p = 1
|
|
+-----+-----+
| |
i = 4 i = 5
p = 3 p = 3

So if I wanted to find all the parent ids from node with index 5 to root I'd
get (3,1)?

As I say, I doubt there is a simple select that can do this but thought I
may as well ask.

Thanks in advance,

Neil Burrows