Concat field result in select query

["Nacef LABIDI" <nacef(dot)l(at)gmail(dot)com>]

Hi all,

I was wondering if there is a way to concatenate the results of a field in a
select to return it as a single string.

Example :

my_field
--------------
1
2
3

select concat_something(my_field) from my_table group by something;
the result expected would be someting like that : 1/2/3 (with a separator it
would be really nice)

I hope that I am not asking for too much ;)

Thanks to all