complex_named_scope.rb

  named_scope :report_options, lambda { |params| 
    {
      :include => :order,
      :joins => [:order => [:redemption, :promo_code]],
      :conditions => 
        [
          params[:before] ? "redemptions.created_at < '#{params[:before]}'" : nil,
          params[:after] ? "redemptions.created_at > '#{params[:after]}'" : nil,
          params[:promo_code] ? "promo_codes.token = '#{params[:promo_code]}'" : nil
        ].compact.join(" AND ")
    }
  }

gistfile2.txt