mysql - Result grouped by resolution with minimum distance from coordinate -


i have query find nearest latitude/longitude given coordinate :

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)               )             )           ) distance         t_fcst_data_coord f                    f.fcst_latitude between :latitude  - (:radius / :distance_unit)           , :latitude + (:radius / :distance_unit)           , f.fcst_longitude between :longitude - (             :radius / (               :distance_unit * cos(                 radians(:latitude)               )             )           )           , :longitude + (             :radius / (               :distance_unit * cos(                 radians(:latitude)               )             )           )         order distance asc         limit 100     ');

the result array ordered distance, , containing resolution of forecast, :

(     [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] => ...         ) )

how can have result shows unique resolution minimum distance order resolution ? expected result :

(     [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         ) )

i tried group fcst_resolution , select min distance, result array wrong latitude , longitudes :

(     [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         )  )

thanks

couple of ways it. normal way use sub query min distance each resolution, , join against query full rows each resolution / distance.

another trick group resolution, , use group_concat each of other fields, ordering distance. use substring_index chop off first occurance of each field result of group_concats. possible issues if contains null, or if field returns value containing comma.

$stmt = $this->db->prepare(' select         substring_index(group_concat(sub0.fcst_latitude order sub0.distance ), ',', 1) fcst_latitude,         substring_index(group_concat(sub0.fcst_longitude order sub0.distance ), ',', 1) fcst_longitude,         sub0.fcst_resolution,         substring_index(group_concat(sub0.distance order sub0.distance ), ',', 1) distance, (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)               )             )           ) distance         t_fcst_data_coord f                    f.fcst_latitude between :latitude  - (:radius / :distance_unit)           , :latitude + (:radius / :distance_unit)           , f.fcst_longitude between :longitude - (             :radius / (               :distance_unit * cos(                 radians(:latitude)               )             )           )           , :longitude + (             :radius / (               :distance_unit * cos(                 radians(:latitude)               )             )           )         order distance asc         limit 100 ) sub0 group sub0.fcst_resolution     ');

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