MS SQL Server 2008 Schema Setup:
create table YourTable(DateCol varchar(20))
insert into YourTable values ('08/10/2013'), ('08102013'), ('081013')
Query 1:
select
case len(DateCol)
when 10 then convert(date, DateCol, 103)
when 8 then convert(date, stuff(stuff(DateCol, 5, 0, '/'), 3, 0, '/'), 103)
when 6 then convert(date, stuff(stuff(DateCol, 5, 0, '/'), 3, 0, '/'), 3)
end
from YourTable
| COLUMN_0 |
|------------|
| 2013-10-08 |
| 2013-10-08 |
| 2013-10-08 |