Question

我有一组点，我从中创建了一个多点。

SET @multi_point = ST_GeomFromText('MULTIPOINT(-118.2845938 34.0252385, -118.2867610 34.0221188, -118.2905912 34.0227248, -118.284119 34.021846, -118.2864676 34.0186438, -118.2886342 34.0203211, -118.2907290 34.0193680, -118.2831326 34.0192874, -118.2828242 34.0205473)');

我还有另外一点

SET @home = ST_GeomFromText('POINT(-118.2819136 34.0261177)')

从@home我想找到最接近的3分。这是多点@multi_point的一部分。我想到了首先使用ST_DISTANCE确定从这个点@home到多点中每个点的距离。但我得到以下内容：

SELECT ST_DISTANCE(@home, @multi_point)

+----------------------------------+
| ST_DISTANCE(@home, @multi_point) |
+----------------------------------+
|            0.0028207205958764945 |
+----------------------------------+

看起来我只得到点到多点的最短距离。问题：

有没有办法让每个点的最短距离，并自己确定点？
是否有更好的方法可以确定@home中某点@multi_point与其余点的最近邻居？

编辑我试过Paul Spiegel将这些点存入一张桌子。但是当我存储Point类型时，它将存储为垃圾值：

+-----------------+---------------------------+
| Name            | Coordinates               |
+-----------------+---------------------------+
| P1              |        [2]pxA@            |
| p2              |        +1Z]:PA@           |
| p3              |        a]KA@              |
| p4              |        X ]qgpA@           |
| p5              |        EW3|U]A@           |
| p6              |        M]bKzA@            |
| p7              |        Ku/]2ƇA@           |
| p9              |        =];A@              |
| p8              |        u`x]A@             |
+-----------------+---------------------------+

此外，当我查询它时，距离为空。

SELECT P.Name, ST_DISTANCE(@home, P.Coordinates) AS dist 
FROM Placemark P ORDER BY dist LIMIT 3;

+--------------+------+
| Name         | dist |
+--------------+------+
| p1           | NULL |
| p2           | NULL |
| p3           | NULL |
+--------------+------+

我该如何解决这个问题？

Answer 1

以下是使用临时表的示例：

drop temporary table if exists Placemark;
create temporary table Placemark(
    Name varchar(50),
    Coordinates point
);

insert into Placemark(Name, Coordinates) values
    ('p1', POINT(-118.2845938, 34.0252385)),
    ('p2', POINT(-118.2867610, 34.0221188)),
    ('p3', POINT(-118.2905912, 34.0227248)),
    ('p4', POINT(-118.284119 , 34.021846 )),
    ('p5', POINT(-118.2864676, 34.0186438)),
    ('p6', POINT(-118.2886342, 34.0203211)),
    ('p7', POINT(-118.2907290, 34.0193680)),
    ('p8', POINT(-118.2831326, 34.0192874)),
    ('p9', POINT(-118.2828242, 34.0205473));

SET @home = ST_GeomFromText('POINT(-118.2819136 34.0261177)');

SELECT 
    P.Name,
    ST_AsText(P.Coordinates) as Coordinates,
    ST_DISTANCE(@home, P.Coordinates) AS dist 
FROM Placemark P
ORDER BY dist
LIMIT 3

结果：

Name | Coordinates                    | dist
p1   | POINT(-118.2845938 34.0252385) | 0.00282072059587649
p4   | POINT(-118.284119 34.021846)   | 0.00480741199088132
p9   | POINT(-118.2828242 34.0205473) | 0.00564433773972052

演示：http://rextester.com/GMPK57301

要定义POINT，请使用POINT(-118.2845938, 34.0252385)或ST_GeomFromText('POINT(-118.2845938 34.0252385)')。要以可读的形式查看值，请使用ST_AsText()。

从MySQL中的给定点找到最近的点

1 个答案: