Q: Tree traversal with SQL query?

Hi,

Is there any way to do tree traversal with only one SQL query (no
procedure/function)?

CREATE TABLE foo (
  node INTEGER,
  parent INTEGER REFERENCES foo(node)
);

Ideally the output would be a depth-first tree traversal starting at root
(marked by parent == node, for example.)

Obviously, I can do this with "normal" programming and loops, but it bugged
me a while if its at all possible doing this in one query.

cheers
-- vbi

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