Convert Null

i had select the data from the database. The null value are returned.
How can i convert the null value to integer so that i can add some value for it??
Actually i try to use both of this statement but there's nothing come out...when i try to selecte the data in the database, the null value are returned

if rs("max_id") = "NULL" then
id_no = 1
response.write "id_no = " &id_no& "<br>"
end if

and

if rs("max_id") = "" then
id_no = 1
response.write "id_no = " &id_no& "<br>"
end if