foodsoft/db/migrate/20181204000000_clear_invalid_invoices_from_orders.rb

class ClearInvalidInvoicesFromOrders < ActiveRecord::Migration[4.2]
  class Order < ActiveRecord::Base; end

  class Invoice < ActiveRecord::Base; end

  def up
    Order.where.not(invoice_id: Invoice.all).update_all(invoice_id: nil)
  end
end