public LinkedList<User> getMostUsefulUsers(int amount) throws SQLException {
        PreparedStatement statement = connection.prepareStatement(
                "SELECT Username, Name, CreditCard, Address, Phone, IsManager FROM Users " +
                        "ORDER BY (SELECT AVG(Score) FROM Usefulness WHERE Reviewer=Username) DESC " +
                        "LIMIT ?");
        statement.setInt(1, amount);
        ResultSet resultSet = statement.executeQuery();
        LinkedList<User> users = new LinkedList<User>();
        while (resultSet.next()) {
            users.add(new User(resultSet.getString(1), resultSet.getString(2), resultSet.getString(3),
                    resultSet.getString(4), resultSet.getString(5), resultSet.getInt(6) == 1));
        }
        return users;
    }