Let me re-name things and remove the non-relational auto-numbering

CREATE TABLE Catalog
(product_name VARCHAR(20) NOT NULL PRIMARY KEY,
lft INTEGER NOT NULL,
rgt INTEGER NOT NULL);

INSERT INTO Catalog
VALUES
('ELECTRONICS', 1, 20),
('TELEVISIONS', 2, 9),
( 'TUBE', 3, 4),
('LCD', 5, 6),
('PLASMA', 7, 8),
('PORTABLE ELECT', 10, 19),
('MP3 PLAYERS', 11, 14),
('FLASH', 12, 13),
('CD PLAYERS', 15, 16),
('2 WAY RADIOS', 17, 18);

SELECT X.product_name, X.lvl,
ROW_NUMBER() OVER (PARTITION BY lvl ORDER BY
X.product_name) AS sorting
FROM (SELECT Children.product_name, (COUNT(Parents.product_name) -
1) AS lvl
FROM Catalog AS Children, Catalog AS Parents
WHERE Children.lft BETWEEN Parents.lft AND
Parents.rgt
GROUP BY Children.product_name) AS X (product_name,
lvl)
ORDER BY lvl, sorting;

This numbers the items horizontally across the tree:

product name lvl sorting
===========================
ELECTRONICS 0 1
PORTABLE ELECT 1 1
TELEVISIONS 1 2
2 WAY RADIOS 2 1
CD PLAYERS 2 2
LCD 2 3
MP3 PLAYERS 2 4
PLASMA 2 5