Grouping null and empty values as one in sql

Question

I have a query which provides a breakdown of different categories applied to things in the database:

select categories, count(*) from products 
group by categories

The data comes like this:

NULL                56
                    42
FooCategory         12
BlahCategory        2

I would like to group NULL and <blank>

NoCategory          98
FooCategory         12
BlahCategory        2

Answer 1

try

select ISNULL(categories,'') as Categories, count(*) from products 
group by ISNULL(categories,'')

UPDATE

see here for parameters required

ISNULL ( check_expression , replacement_value )

Answer 2

try

select categories, 
case when categories is null or categories = ' ' 
then 'noCategory' else categories end as grouped,
count(*) 
from products 
group by grouped