CREATE FUNCTION dbo.is_installed (@prod_code int)
RETURNS int
AS
BEGIN
    if @prod_code IS NULL
        return 0

    declare @count integer
    set @count = (SELECT count(*)
                    FROM ca_application_registration
                   WHERE product_code = @prod_code)
                          
    if @count >= 1
        return 1
    return 0
END
GO