Insert new record to sqlserver db problem(ruby 1.8.6, Rails 1.2.3)

Hi,

I have a model name called 'Address' with 4
column(id,code,details,active).

Here i declared in Model.rb
set_primary_key :code.
and map these code to others table(association) and id is serial not primary key.

now i am not able to create new record for address table (giving input for
code, details, active).

i am getting below error

code is not null..

Code value is will not taken  and cann't insert value to table.

Any help would be appreciated..

Thanks & Regards,
sathiya.rails