If you use nchar(n) for a column, say n=5 and the length of the string you enter for this column is 3. MS SQL adds whitespace to this string to make it 5 characters long. Be mindful of that, this can break a DropDownList when you try to assign this string as the SelectedValue and the dropdownlist is pre-populated manually or from a different source.
I of course learnt this the hard way after spending considerable time.