connecting model class to different column name other tn id

I am using the allready created tables in oracle and connecting to the
ruby on rails model class, i used 'set_table_name 'table name' ' and it
gets connected but, i want to access its records and it has different id
field name as field_id, i want to access its record making field_id
field as my id field so that i can access its records but i dont want to
rename field_id to id sence, it has laks of records and my company is
using those records can any one sugust me the way to connect the model
to field_id column...plz help

Thanks in advance...
with regards,

Use the set_primary_key method.

Siddick Ebramsha wrote:

Use the set_primary_key method.

I used this method as follows

class Item < ActiveRecord::Base
  set_table_name 'item'
  set_primary_key 'id_field'

and now its working properly,
Thanks you,
for your good response!!!!!!
Keep responding me.....