get branches & childs from database

Hello newsgroup!

I'm trying to build up a menu by sending ONE query to database.
Afterwards the result is used by PEAR::HTML_Menu get
a html-structered menu.

db-structure of gallery:
+----+-------+------+------+--------+-------+
| id | title | date | root | parent | level |
+----+-------+------+------+--------+-------+
| 5 | A | XX | 5 | 0 | 1 |
| 1 | A2 | XX | 5 | 5 | 2 |
| 2 | A1 | XX | 5 | 5 | 2 |
| 3 | A11 | XX | 5 | 2 | 3 |
| 4 | A12 | XX | 5 | 2 | 3 |
| 6 | A21 | XX | 5 | 1 | 3 |
| 7 | A211 | XX | 5 | 6 | 4 |
| 8 | B | XX | 8 | 0 | 1 |
| 9 | B1 | XX | 8 | 8 | 2 |
+----+-------+------+------+--------+-------+

following limitations are set:
- for root-nodes parent=0 have to be set
- result should by available after sending ONE query
- child of the specified gallery should be delivered
- branch of the specified gallery should be delivered

menu-structure after the query for id=6:

+ A
|-> A1 (optional, no need to be but nice to have)
|-> A2
|-> A21 (specified id)
|-> A211
+ B

Therefore I need the following result after sending the query:

+----+-------+--------+
| id | title | parent |
+----+-------+--------+
| 8 | B | 0 |
| 6 | A21 | 1 |
| 7 | A211 | 6 |
| 1 | A2 | 5 |
| 5 | A | 0 |
| 2 | A1 | 5 | (optional)
+----+-------+--------+

I currently use following query:

SELECT id,title,parent,FROM gallery
WHERE (id=root OR root IN
(SELECT root FROM gallery WHERE id=6))
AND gall_level <= (SELECT level FROM gallery WHERE id=6)+1
ORDER BY level ASC,date DESC

With this query I get the additional branch under A1, but that's not
what I want. I don't know what to do.
I'm able to use views, subselects, rules (of course) and furthermore
functions (plpgsql).

I'd be pleased, if there are any ideas

Thanks, Marcus.