Exluding lines within a WHERE clause in a SP

Hello,

I am passing several selection parameters to a stored procedure, and I would like to exclude particular lines within the where clause of the stored procedure if those parameters are set to a particular value.

Below is a snippet (that doesn't work) from the stored procedure. Notice in particular the bits using the IN keyword. Instead of passing the entire list when the user selects the "all" checkbox, I would like to just pass the word "all" and not even mess with including the part of the WHERE clause that uses the IN keyword.

I have a bad feeling that I cannot do this, and I will instead have to type in multiple where statements.



WHERE a.signature = 1
AND b.Date between @begindate and @enddate
if classBillingcode != 'all'
AND classBillingcode IN (@billingcodelist) --use for parameters
if classBillingcode != 'all'
AND tblTraineeTypecode IN (@traineetypelist)-- use for parameters

you are testing classBillingcode in SP logic, but it appears that it is a table column

rudy