gistfile1.txt

    monthly_data = book.monthly_data.order("call_date DESC")
    price_data = book.price_data.order("date DESC")
    price_data.each do |row|
      catch :skip_row do
        row_date = row.date.to_date
        case 
        when row_date > monthly_data.first.call_date
          row.update_attributes(:monthly_datum_id => monthly_data.first.id)
        when row_date == monthly_data.first.call_date  
          monthly_data.shift
          throw :skip_row
        when row_date < monthly_data.first.call_date
          monthly_data.shift
        end
      end
    end