if object_id ('test') is not null
begin
	drop table test
end
create table test
(
	test_string varchar ( 32 ),
	test_string1 varchar ( 32 )
)
insert into test (test_string, test_string1) values ('aaa', 'a')
insert into test (test_string, test_string1) values ('bbb', 'z')
insert into test (test_string, test_string1) values ('aaa', 'b')
insert into test (test_string, test_string1) values ('bbb', 'x')
insert into test (test_string, test_string1) values ('ccc', 'q')
insert into test (test_string, test_string1) values ('aaa', 'c')
go
if object_id ('GetTest') is not null
begin
	drop function dbo.GetTest
end
go
create function dbo.GetTest
(
	@test_string varchar( 32 )
)
returns varchar ( 1024 )
as
begin
	declare @Result varchar( 8000 )
	set @Result = ''
	select @Result = @Result + test_string1 + ' ' from dbo.test WHERE test_string = @test_string
	return rtrim(@Result)
end
GO
select test_string, dbo.GetTest(test_string)
from test
group by test_string