create table t1(c1 int, u1 int)

insert into t1
select 1, 2 union all
select 1, 3 union all
select 2, 2 union all
select 1, 5


-- 第一个问题：检索
select t.c1,
left(
cast((select cast(u1 as varchar(1))+',' from t1 where c1=t.c1 for xml path('')) as varchar(10)),
len(cast((select cast(u1 as varchar(1))+',' from t1 where c1=t.c1 for xml path('')) as varchar(10)))-1) u1
from t1 t
where t.c1=1
group by t.c1

c1          u1
----------- ----------
1           2,3,5

(1 row(s) affected)


-- 第二个问题是：插入新数据集
declare @c int,@u varchar(10)

-- 传入的参数
select @c=1,@u='2,3,7,9'

insert into t1
select t2.* 
from 
(select a.c0,
substring(a.u0,b.number,charindex(',',a.u0+',',b.number)-b.number) u0
from (select @c c0,@u u0) a
inner join master.dbo.spt_values b
on b.[type]='p'
and substring(','+a.u0,b.number,1) = ',') t2
left join t1 on t2.c0=t1.c1 and t2.u0=t1.u1
where t1.u1 is null 

select * from t1 where c1=1

c1          u1
----------- -----------
1           2
1           3
1           5
1           7
1           9

(5 row(s) affected)