Ruby on Rails

Hi,
 I have two models named Customer and Order.

Customer < ActiveRecord::Base
has_many :orders
end

Order < ActiveRecord::Base
belongs_to :customer
end

Customer model has attributes like first_name and last_name. Order has customer_id along with other attributes.

Now, I want Customer first_name for specific order. I can get it with following query.

Customer.joins(:orders).where('orders.id = 1').select('first_name').

But, how to get it along with attributes of order table also. Say, I want both customers first_name and orders table created_at value.
When I try,
Order.includes(:customer).select('orders.created_at, customers.first_name')
this returns only order table records. What is the best way to select attributes of joined tables also with Active Record Query.

Thanks.