create table result1 (pid int,res varchar( 8000 ))
go
create function [dbo].[fn_strSum] (@PID int, @separator char( 1 )) 
returns varchar( 8000 )
as
begin
	declare @result varchar( 8000 )
	set @result = ''
	
	select @result = coalesce(t3.CName,'') + @separator + @result
	from Titles t1
	inner join TitlesCategories t2
	on t1.PID = t2.PID
	inner join Categories t3
	on t2.CID = t3.CID
	where t1.PID = @PID

if Len(@result) >  0 
	set @result =  substring(@result,  1 , len(@result)- 1 )
else
	set @result = null
return @result
end
go
insert into result1 select PID, [dbo].[fn_strSum] (PID, ',')  from Titles

select * from result1 where res is not null

drop function [dbo].[fn_strSum]

drop table result1

create table result2 (pid int,cname varchar( 200 ),res varchar( 7800 ))

create unique clustered index ix_result2 on result2 (pid,cname)

insert into result2 select t1.pid,t2.cname,'' from TitlesCategories t1
inner join Categories t2 on t1.CID=t2.CID
order by t1.pid,t2.cname

declare @Contact varchar( 8000 ),@PID int
set @Contact = '' set @pid= 0 

update result2 set @Contact=res=case when @PID=PID then CName+','+@Contact else CName end, @PID=PID

select pid,max(res) from result2 group by pid

drop table result2

create table result3 (PID int, Res varchar( 8000 )) 
go 
set nocount on
go
declare @PID int, @CID int, @CName varchar( 20 ), @Result varchar( 255 ) 

declare TitleCur cursor for 
select PID from Titles 
open TitleCur 
fetch TitleCur into @PID

while @@fetch_status =  0  
begin 
declare CatCur cursor for 
select c.CID, c.CName from Categories c join TitlesCategories tc on tc.CID = c.CID and PID = @PID 

open CatCur 
set @Result = '' 
fetch CatCur into @CID, @CName 
while @@fetch_status =  0  
begin 
set @Result = @Result + case @Result when '' then '' else ', ' end + @CName 
fetch CatCur into @CID, @CName 
end 
insert into result3 values (@PID, @Result) 
deallocate CatCur 
fetch TitleCur into @PID
end 
select * from result3 
deallocate TitleCur 

drop table result3