delete duplicate strings in different records

IF OBJECT_ID('tb') IS NOT NULL
DROP TABLE tb
GO
CREATE TABLE tb( a varchar(30))
go
insert tb SELECT '001,003,008'
UNION ALL SELECT '003,008,019'
go
declare @s varchar(40)
select @s=isnull(@s+',','')+a from (
Select distinct
a=substring(a.a,b.number,charindex(',',a.a+',',b.number)-b.number)
from
tb a join master..spt_values  b
ON B.type='p' AND B.number BETWEEN 1 AND LEN(A.a)
where
substring(','+a.a,b.number,1)=',') t
DROP TABLE tb
select @s as Result