declare @test table (first_name varchar(10), last_name varchar(10), address varchar(100), code int)
insert into @test
	select 'Cindy','Lair','111 Drury Circle Harrisburg Pennsylvania',717 union
	select 'Cindy','Lair','111 Drury Circle Harrisburg Pennsylvania',716 union
	select 'Cindy','Lair','111 Drury Circle Harrisburg Pennsylvania',715 

select 	t1.first_name,
	t1.last_name,
	t1.address,
	isnull(cast(max(t1.code) as varchar),'') + 
	isnull(',' + cast(max(t2.code) as varchar),'') + 
	isnull(',' + cast(max(t3.code) as varchar),'') as 'code'
from @test t1 
left join @test t2 
	on t1.first_name = t2.first_name
	and t1.last_name = t2.last_name
	and t1.address = t2.address
	and t1.code > t2.code
left join @test t3 
	on t1.first_name = t3.first_name
	and t1.last_name = t3.last_name
	and t1.address = t3.address
	and t2.code > t3.code
group by t1.first_name, t1.last_name, t1.address

declare @results table (test_id int, first_name varchar(10), last_name varchar(10), address varchar(100), code varchar(5), code_csv varchar(8000))
insert into @results (test_id, first_name, last_name, address, code)
	select 1,'Cindy','Lair','111 Drury Circle Harrisburg Pennsylvania',717 union
	select 2,'Cindy','Lair','111 Drury Circle Harrisburg Pennsylvania',716 union
	select 3,'Cindy','Lair','111 Drury Circle Harrisburg Pennsylvania',715 union
	select 4,'Nathan','Skerl','1234 Main',111 union
	select 5,'Nathan','Skerl','1234 Main',112

select * from @results

-------------------------------------------------------------------------
-- generate a common id for those with matching names, address, etc.
-------------------------------------------------------------------------
update r
set test_id = d.test_id
from @results r inner join (select min(test_id) test_id, first_name, last_name, address from @results group by first_name, last_name, address) d
	on r.first_name = d.first_name
	and r.last_name = d.last_name
	and r.address = d.address

-------------------------------------------------------------------------
-- ** set based method from: [url]http://www.sqlteam.com/item.asp?ItemID=11021[/url]
-------------------------------------------------------------------------
declare	@code varchar(8000),
	@last_id int

select	@code = '',
	@last_id = -1

update @results
set @code = code_csv = case
                       when @last_id <> test_id then code
                       else @code + ', ' + code
                   end,
    @last_id = test_id

-------------------------------------------------------------------------
-- results
-------------------------------------------------------------------------
select 	first_name,
	last_name,
	address,
	convert(varchar(200),max(code_csv)) code_csv
from @results
group by first_name, last_name, address

quote:

---

1124....10
............12

1122....15
............16
............17

1111....10
............11

---