public void updateWyniki(int idProduktu, String ilosc) {
        String sql = "Select ilosc from magazyn where idProduktu =" + idProduktu;
        int counter = ilosc;
        try {
            ResultSet rs = st.executeQuery(sql);
            while (rs.next()) {
				counter += rs.getInt("ilosc");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        sql = "UPDATE magazyn set ilosc = " + counter + " where idProduktu =" + idProduktu;
        executeUpdate(sql);
}