PostgreSQL recursive with - sql

Question

I need help with a recursive query. Assuming the following table:
CREATE TEMPORARY TABLE tree (
id integer PRIMARY KEY,
parent_id integer NOT NULL,
name varchar(50)
);
INSERT INTO tree (id, parent_id, name) VALUES (3, 0, 'Peter'), (2,0, 'Thomas'), (5,2, 'David'), (1, 0, 'Rob'), (8, 0, 'Brian');
I can retrieve a list of all people and their children with the following query:
WITH RECURSIVE recursetree(id, parent_id) AS (
SELECT id, parent_id FROM tree WHERE parent_id = 0
UNION
SELECT t.id, t.parent_id
FROM tree t
JOIN recursetree rt ON rt.id = t.parent_id
)
SELECT * FROM recursetree;
How can I list them in order, and also sort the first level items by name? For example, the desired output would be:
id, parent_id, name
8, 0, "Brian"
3, 0, "Peter"
1, 0; "Rob"
2, 0, "Thomas"
5, 2, " David"
Thanks,
**EDIT. Please note that adding an ORDER BY won't work: **
WITH RECURSIVE recursetree(id, parent_id, path, name) AS (
SELECT
id,
parent_id,
array[id] AS path,
name
FROM tree WHERE parent_id = 0
UNION ALL
SELECT t.id, t.parent_id, rt.path || t.id, t.name
FROM tree t
JOIN recursetree rt ON rt.id = t.parent_id
)
SELECT * FROM recursetree ORDER BY path;
The above will retain the parent child relationship (children follow their parents), but applying any other ORDER BY clause (ie: name - like some have suggested) will cause the result to lose it's parent-child relationships.

Answer 1

See also this (translated) article about CTE's in PostgreSQL: wiki.phpfreakz.nl
Edit: Try this one, using an array:
WITH RECURSIVE recursetree(id, parent_ids, firstname) AS (
SELECT id, NULL::int[] || parent_id, name FROM tree WHERE parent_id = 0
UNION ALL
SELECT
t.id,
rt.parent_ids || t.parent_id,
name
FROM tree t
JOIN recursetree rt ON rt.id = t.parent_id
)
SELECT * FROM recursetree ORDER BY parent_ids;

Answer 2

You can add a path to your query and order by it at the end:
WITH RECURSIVE recursetree(id, parent_id,path) AS (
SELECT id, parent_id,id||'' as path FROM tree WHERE parent_id = 0
UNION
SELECT t.id, t.parent_id,concat(rt.path,'_',t.id)
FROM tree t
JOIN recursetree rt ON rt.id = t.parent_id
)
SELECT * FROM recursetree
ORDER BY rt.path;