Group_concat for MS SQL

group_concat

Tables: 
a (id, name)
b (id, name)
a_to_b (a_id, b_id)

Outputs:
a_id a_name b_ids_over_comma

select *, STUFF( 
    (SELECT ',' + LTRIM(RTRIM(b.name))
	 FROM b b join a_to_b on b_id = b.id
	 WHERE a_id = a.id
	 FOR XML PATH('')
	),
1, 1, '') group_concat from a a