declare @table table (id VARCHAR(2),c_n VARCHAR(14) )
insert into @table
select '1','2' union all
select '2','2,2,3,4,5' union all
select '3','2'

select * from @table where CHARINDEX('2',c_n)>0 
/*
id   c_n
---- --------------
1    2
2    2,2,3,4,5
3    2
*/

select * from @table where c_n LIKE '%2%'
/*
id   c_n
---- --------------
1    2
2    2,2,3,4,5
3    2
*/

select * from @table where  LEN(REPLACE(c_n,'2',''))<LEN(c_n)
/*
id   c_n
---- --------------
1    2
2    2,2,3,4,5
3    2
*/

--上面的情况都是后面有例如'22,3,4,5,7'也算是有'2'

--只取单独为2的：
go

declare @table table (id VARCHAR(2),c_n VARCHAR(14) )
insert into @table
select '1','29,3' union all
select '2','1,2,3,4,5' union all
select '3','25,4,22'

select * from @table where  ','+c_n+',' LIKE '%,2,%'
/*
id   c_n
---- --------------
2    1,2,3,4,5
*/

------解决方案--------------------


------解决方案--------------------
select * from ttt  where CHARINDEX('2',c_n)>0  


------解决方案--------------------

SQL code

create table #t
(
id int not null identity(1,1) primary key,
cn varchar(100) not null
)

/*
id c_n
1 2
2 2,2,3,4,5
3 2
*/

insert into #t
values
('2'),
('2,2,3,4,5'),
('2')

select * from #t
where CHARINDEX('2',cn,1)>0

drop table #t

------解决方案--------------------
你没有理解in的含义.多看看书.