SQL Server convert select a column and convert it to a string

select  stuff(list,1,1,'')
from    (
        select  ',' + cast(col1 as varchar(16)) as [text()]
        from    YourTable
        for     xml path('')
        ) as Sub(list)

Example at SQL Fiddle.

There is new method in SQL Server 2017:

SELECT STRING_AGG (column, ',') AS column FROM Table;

that will produce 1,3,5,9 for you

You can do it like this:

Fiddle demo

declare @results varchar(500)

select @results = coalesce(@results + ',', '') +  convert(varchar(12),col)
from t
order by col

select @results as results

| RESULTS |
-----------
| 1,3,5,9 |