dbsteup.rb

require 'sqlite3'
require 'active_record'

ActiveRecord::Base.logger = Logger.new(STDERR)
ActiveRecord::Base.establish_connection(
  :adapter  => 'sqlite3',
  :database => 'dbfile_example'
)


class CreateProducts < ActiveRecord::Migration
  def change
    create_table :products do |t|
      t.belongs_to :vendor, index: true
      t.string     :name
      t.integer    :instock
    end
  end
end

class CreateVendors < ActiveRecord::Migration
  def change
    create_table :vendors do |t|
      t.string :name
    end
  end
end

class CreateSales < ActiveRecord::Migration
  def change
    create_table :sales do |t|
      t.belongs_to :employee, index: true
      t.belongs_to :product,  index: true
      t.time :date
    end
  end
end

class CreateEmployee < ActiveRecord::Migration
  def change
    create_table :employees do |t|
      t.string   :name
    end
  end
end

class Product < ActiveRecord::Base
  belongs_to :vendor
  has_many   :sales
end

class Vendor < ActiveRecord::Base
  has_many :products
end

class Sale < ActiveRecord::Base
  belongs_to :emplopyee
  belongs_to :product
end

class Employee < ActiveRecord::Base
  has_many :sales
end