Dynamic Parameter to incliude Null values

[GCL2007]

Not sure if there is a way to handle this. Have a Dynamic Parameter based on Product Type field (Crystal XI). Report works fine - but there are a number of entries in database with Null value in Product Type field. Would like the parameter selection when the report is run to include an option for 'null' in addition to the product types it finds. Any one have any ideas on how best to do this?
Thanks

 

[lbass]

Use a command to populate the dynamic parameter picklist:

select table.ProductType
from table
union
select ' Null'
from table

The space will force ' Null' to be at the top of the list. Then create a record selection formula like this:

(
(
{?ProdType} = ' Null' and
isnull({table.producttype})
) or
{table.producttype} = {?ProdType}
)

Be sure NOT to reference the command field in the body of the report.

-LB