group_concat equivalent

group_concat.sql

SELECT
    G.GROUP_ID,
    G.GROUP_NAME,
    stuff(
    (
    select cast(',' as varchar(max)) + U.USERNAME
    from USER_GROUPS U
    WHERE U.GROUP_ID = G.GROUP_ID
    order by U.USERNAME
    for xml path('')
    ), 1, 1, '') AS USERS
FROM
    GROUPS G
ORDER BY
    G.GROUP_NAME ASC;