mysql-选择彼此之间相距较近的记录 [英] mysql - select records with near distance from each other

问题描述

我有一个包含位置的mysql表，例如:

I have a mysql table containing locations, for example:

ID  latitude  longitude  value
1   11.11111  22.22222   1
2   33.33333  44.44444   2
3   11.11112  22.22223   5

我想选择彼此靠近的记录(在上面的示例中，第1行和第3行)，以便可以将它们作为一个记录插入到新表中.说近就说100米.我希望新表是:

I want to select records which are located near to each other (in the above example, rows 1 and 3), so that I can insert them in a new table as one record. By saying near, let's say 100 meters. I would like the new table to be:

ID  latitude  longitude  value   
1   11.11111  22.22222   3
2   33.33333  44.44444   2

如您所见，我想保留第一条记录的坐标，并在值"列中插入两条记录的平均值.

As you can see, I would like to keep the coordinates of the first record and insert an average of the two records in column 'value'.

我用于距离的公式如下:

The formula I use for distance is the following:

R*SQRT(((lon2*c-lon1*c)*cos(0.5*(lat2*c+lat1*c)))^2 + (lat2*c-lat1*c)^2)

其中

[lat1, lon1] the coordinates of the first location,
[lat2, lon2] the coordinates of the second location,
[R] the average radius of Earth in meters,
[c] a number to convert degrees to radians.

该公式适用于短距离.

所以，我的问题不是lat，lon到距离的转换，而是我的SQL.我知道如何选择与特定纬度，经度坐标之间最大距离为100米的记录，但是我不知道如何选择彼此之间最大距离的记录.

So, my problem is not the conversion of lat,lon to distances but my SQL. I know how to select records that have a maximum distance of 100 meters from specific lat,lon coordinates but I dont know how to select records with a maximum distance from each other.

我做到这一点的一种方法(它确实有效)是通过在PHP中逐个循环记录，然后对每个记录进行循环，通过SQL查询选择附近的记录.但是通过这种方式，我循环执行了一个SQL查询，据我所知，这是一种不好的做法，尤其是当记录要成千上万的时候.

One way I did it -and it works- is by looping the records one by one in PHP and for each one, making an SQL query to select records that are near. But this way, I do an SQL query in a loop and as far as I know, this is a bad practice, especially if the records are gonna be thousands.

我希望我很清楚.如果没有，我很乐意为您提供更多信息.

I hope I was clear. If not, I would be glad to give you additional information.

感谢您的帮助.

推荐答案

下面是一条SQL，用于获取该范围内的所有位置:

Here is a SQL to get all places within the range:

SELECT 
    ID,
    latitude,
    longitude,
    (6371 * acos (cos( radians(origin.latitude)) * cos( radians( destination.latitude )) 
        * cos( radians(destination.longitude) - radians(origin.longitude)) + sin(radians(origin.latitude)) 
        * sin( radians(destination.latitude)))) AS distance
FROM myTable as destination, myTable as origin
WHERE destination.id = myId
HAVING distance < 100 --some value in kilometers

6371是千米的常数.3959是常数.

6371 is a constant for kilometers. 3959 is a constant for miles.

本主题有更多答案: MySQL大圆距离(Haversine公式)

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