How to get a result in one row

Hi!

I'm using PostgreSQL 7.4.7.

table_c
id | nick
----+------
1 | T
2 | S
3 | G
4 | A
5 | D
...

table_m
id | c
------+----
22192 | 4
15041 | 3
21764 | 5
22192 | 1
15041 | 4
15041 | 2
...
where table_m.c is a foreign key on table_c.id

SELECT table_m.id,table_c.nick
FROM table_m AS m JOIN table_c AS c ON c.id=m.c
WHERE m.id=22192
ORDER BY c.nick;

returns:
id | nick
------+------
22192 | A
22192 | T
(2 rows)

I'd like to get the result in only one row:
id | nick
------+------
22192 | A,T

(and similarly: 15041 | A,G,S )

As table_c can increase, I don't want to use the case construct.
How can I do? Maybe writing a function. But how?

TIA!

virgi