结果按分辨率分组，距坐标的最小距离

Question

我有一个查询要从给定坐标找到最近的 latitude/longitude :

public function findClosestByLatitudeLongitude($latitude, $longitude, $distanceUnit = 111.045, $radius = 150)

$stmt = $this->db->prepare('SELECT
        f.fcst_latitude,
        f.fcst_longitude,
        f.fcst_resolution,
        :distance_unit * DEGREES(
            ACOS(
              COS(
                RADIANS(:latitude)
              ) * COS(
                RADIANS(f.fcst_latitude)
              ) * COS(
                RADIANS(:longitude) - RADIANS(f.fcst_longitude)
              ) + SIN(
                RADIANS(:latitude)
              ) * SIN(
                RADIANS(f.fcst_latitude)
              )
            )
          ) AS distance
        FROM t_fcst_data_coord AS f
        WHERE 
          f.fcst_latitude BETWEEN :latitude  - (:radius / :distance_unit)
          AND :latitude + (:radius / :distance_unit)
          AND f.fcst_longitude BETWEEN :longitude - (
            :radius / (
              :distance_unit * COS(
                RADIANS(:latitude)
              )
            )
          )
          AND :longitude + (
            :radius / (
              :distance_unit * COS(
                RADIANS(:latitude)
              )
            )
          )
        ORDER BY distance ASC
        LIMIT 100
    ');

结果是一个按距离排序的数组，其中包含预测的分辨率，如下所示：

(
    [0] => Array
        (
            [fcst_latitude] => 46.295396
            [fcst_longitude] => 6.854558
            [fcst_resolution] => 9.0
            [distance] => 1.2113482186062683
        )

    [1] => Array
        (
            [fcst_latitude] => 46.313622
            [fcst_longitude] => 6.843681
            [fcst_resolution] => 3.0
            [distance] => 1.4198633375521186
        )

    [2] => Array
        (
            [fcst_latitude] => 46.314401
            [fcst_longitude] => 6.884638
            [fcst_resolution] => 3.0
            [distance] => 2.213273758077741
        )

    [3] => Array
        (
            [fcst_latitude] => 46.285180
            [fcst_longitude] => 6.844827
            [fcst_resolution] => 3.0
            [distance] => 2.5347004607874783
        )

    [...] => Array
        (
            [fcst_latitude] => ...
            [fcst_longitude] => ...
            [fcst_resolution] => ...
            [distance] => ...
        )

    [53] => Array
        (
            [fcst_latitude] => 46.199091
            [fcst_longitude] => 6.886765
            [fcst_resolution] => 27.0
            [distance] => 12.064028782357124
        )

    [...] => Array
        (
            [fcst_latitude] => ...
            [fcst_longitude] => ...
            [fcst_resolution] => ...
            [distance] => ...
        )
)

我怎样才能得到一个只显示唯一分辨率且按分辨率排序的最小距离的结果？预期结果是：

(
    [0] => Array
        (
            [fcst_latitude] => 46.199091
            [fcst_longitude] => 6.886765
            [fcst_resolution] => 27.0
            [distance] => 12.064028782357124
        )

    [1] => Array
        (
            [fcst_latitude] => 46.295396
            [fcst_longitude] => 6.854558
            [fcst_resolution] => 9.0
            [distance] => 1.2113482186062683
        )

    [2] => Array
        (
            [fcst_latitude] => 46.313622
            [fcst_longitude] => 6.843681
            [fcst_resolution] => 3.0
            [distance] => 1.4198633375521186
        )
)

我尝试按 fcst_resolution 和 select 最小距离进行 GROUP BY，但结果是一个经纬度错误的数组：

(
    [0] => Array
        (
            [fcst_latitude] => 44.972113
            [fcst_longitude] => 8.737022
            [fcst_resolution] => 9.0
            [distance] => 1.2113482186062683
        )

    [1] => Array
        (
            [fcst_latitude] => 45.231748
            [fcst_longitude] => 5.680505
            [fcst_resolution] => 3.0
            [distance] => 1.4198633375521186
        )

    [2] => Array
        (
            [fcst_latitude] => 45.118703
            [fcst_longitude] => 8.640296
            [fcst_resolution] => 27.0
            [distance] => 12.064028782357124
        )

)

谢谢

Answer 1

有几种方法可以做到。正常方法是使用子查询获取每个分辨率的最小距离，然后将其与查询结合起来以获得每个分辨率/距离的完整行。

另一个技巧是按分辨率分组，然后对每个其他字段使用 GROUP_CONCAT，按距离排序。然后使用 SUBSTRING_INDEX 从 GROUP_CONCAT 的结果中删除每个字段的第一次出现。如果任何内容包含 NULL，或者如果任何字段 returns 包含逗号的值。

可能会出现问题

$stmt = $this->db->prepare('
SELECT
        SUBSTRING_INDEX(GROUP_CONCAT(sub0.fcst_latitude ORDER BY sub0.distance ), ',', 1) AS fcst_latitude,
        SUBSTRING_INDEX(GROUP_CONCAT(sub0.fcst_longitude ORDER BY sub0.distance ), ',', 1) AS fcst_longitude,
        sub0.fcst_resolution,
        SUBSTRING_INDEX(GROUP_CONCAT(sub0.distance ORDER BY sub0.distance ), ',', 1) AS distance,
FROM
(SELECT
        f.fcst_latitude,
        f.fcst_longitude,
        f.fcst_resolution,
        :distance_unit * DEGREES(
            ACOS(
              COS(
                RADIANS(:latitude)
              ) * COS(
                RADIANS(f.fcst_latitude)
              ) * COS(
                RADIANS(:longitude) - RADIANS(f.fcst_longitude)
              ) + SIN(
                RADIANS(:latitude)
              ) * SIN(
                RADIANS(f.fcst_latitude)
              )
            )
          ) AS distance
        FROM t_fcst_data_coord AS f
        WHERE 
          f.fcst_latitude BETWEEN :latitude  - (:radius / :distance_unit)
          AND :latitude + (:radius / :distance_unit)
          AND f.fcst_longitude BETWEEN :longitude - (
            :radius / (
              :distance_unit * COS(
                RADIANS(:latitude)
              )
            )
          )
          AND :longitude + (
            :radius / (
              :distance_unit * COS(
                RADIANS(:latitude)
              )
            )
          )
        ORDER BY distance ASC
        LIMIT 100
) sub0
GROUP BY sub0.fcst_resolution
    ');

结果按分辨率分组，距坐标的最小距离

Result grouped by resolution with minimum distance from coordinate

mysql

group-by

distance

coordinates