class Order < ActiveRecord::Base
    set_primary_key "OrderID"
    has_one  :customer
    has_many :packages, :foreign_key => "orderid"
end

class Package < ActiveRecord::Base
    set_table_name "Package"
    set_primary_key "packageid"
    belongs_to :order,
               :foreign_key => "orderid"
end

MSSQL Tables:
orders                                  package
+++++++++++++++++++++++                ++++++++++++++++++++++++++++++++++
OrderID (pk)                           packageid (pk)
CustomerID                             weight
ShipDate                               orderid (fk)
                                       postalused
                                       mailclassused