Queries for Nested Set Model

So this is just a follow up post to my Nested Set Model post to document the scheme/queries that I'm using to define my tree. I created a node with id=0 called ROOT (since it's basically just a place holder that I use to do the dirty work and won't ever show the user) and create a UNIQUE constraint on (lft, rgt) to satisfy my obsession with data integrity (and I imagine that it should help speed up the queries as well).

So here's the queries I use to grab the information in useful manners.

Grab the Whole Tree:

SELECT *
FROM bills
ORDER BY lft;

Grabs the Ancestors of a Node:

SELECT parent.*
FROM bills AS node, bills AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rgt
AND node.id = ? AND parent.id <> ? (NOTE: Both ?'s are the same value)
ORDER BY node.lft;

Grabs the Descendents of a Node:

SELECT node.*
FROM bills AS node, bills AS parent
WHERE node.lft > parent.lft AND node.rgt < id =" ?">

Grab the Parent of a Node:

SELECT parent.*
FROM bills AS node, bills AS parent
WHERE node.lft BETWEEN parent.lft AND parent.rgt
AND node.id = ?
ORDER BY parent.lft DESC LIMIT 1,1

Obviously, the '?' is the ID of the node that you're interested in and you can cater the selected columns to your needs.