java - 区分列中的零值和查询结果

Question

我正在尝试获取最小 speed我记录的值(value) 我有案例 速度的值(value)等于0在 speed 栏中但我也有这样的情况，我的查询结果是 0因为在 40 米的范围内没有找到最小速度。如何区分这两种情况？

代码:

    String sql_min_speed = "SELECT mac, stop_name, stop_distance, speed from behaviour "
            + "where stop_distance < 40 and mac = ? and stop_name = ? order by speed LIMIT  1";

    int minSpeed = get_min_speed(macD, con, sql_min_speed, stopName,
            maintain);

get_min_speed 方法:

private int get_min_speed(String macD, Connection con, String sql,
        String stopName, List<Maintain> maintain) throws SQLException {
    PreparedStatement prepared1 = con.prepareStatement(sql);
    prepared1.setString(1, macD);
    prepared1.setString(2, stopName);
    ResultSet rsBehav1 = prepared1.executeQuery();
    int min_speed = 0;
    while (rsBehav1.next()) {
        String mac = rsBehav1.getString("mac");
        String Stname = rsBehav1.getString("stop_name");
        int distance = rsBehav1.getInt("stop_distance");
        min_speed = rsBehav1.getInt("speed");
        Maintain main1 = new Maintain(mac, Stname, distance, min_speed);
        maintain.add(main1);

    }
    return min_speed;
}

Answer 1

将 int min_speed = 0; 更改为 int min_speed = -1;

然后在调用方法中添加一个条件。