SQL Parameter And Wildcards, How To Make It Work?

Hello, I have what should be a very simple problem, but I cant solve it.
I want to have a stored procedure return a table query (no problems here) but I also need to supply several parameters to the stored procedure (again, no problem!)

Here is the problem, I need to be able to supply a wildcard into the stored procedure as an argument somehow. I can do this already, but the results are incorrect!!! It seems like when local variables are used, the wildcard argument gets ignored. for example, I have included the following example:


DECLARE @Dv_id nchar(15)

SET @Drv_id = '%'



SELECT Diver.*, (ROW_NUMBER() OVER(ORDER BY Dv_id)) as RowNum FROM Diver WHERE Dv_id LIKE @Dv_id



SELECT Diver.*, (ROW_NUMBER() OVER(ORDER BY Dv_id)) as RowNum FROM Diver WHERE Dv_id LIKE '%'

OK, this is an example of my problem, the results I get from this are that the fist SELECT return 0 rows.
The second SELECT returns the correct number of rows (everything in the table). Why is there a difference between:
WHERE Drv_id LIKE @Drv_id
and
WHERE Drv_id LIKE '%'
?
The wildcard statement '%' is supposed match everything, correct??
It seems like the local variable SET command syntax eats up my value of '%' and turns it into a NULL.

Is there any way around this?