tap/db/migrate/20150210062809_order_id_null_allowed_in_order_items.rb

class OrderIdNullAllowedInOrderItems < ActiveRecord::Migration
  def up
    change_column :order_items, :order_id, :integer, null: true
  end

  def down
    change_column :order_items, :order_id, :integer, null: false
  end
end