Mysql within distance query

问题

Options

$lat = '25.7742658';
$lng = '-80.1936589';
$miles = 30;

Query

SELECT *, 
   ( 3959 * acos( cos( radians($lat) ) 
   * cos( radians( lat ) ) 
   * cos( radians( lng ) - radians($lng) ) 
   + sin( radians($lat) ) 
   * sin( radians( lat ) ) ) ) AS distance 
FROM locations 
HAVING distance < $miles 
ORDER BY distance 
LIMIT 0, 20

I have a database table with 4 columns:

unique id
city name
latitude (lat)
longitude (lng)

I'm using the query on top to return locations that are within a specified number of miles from the specified coordinates. It seems to work but I'm not sure how accurate it is. I'm curios to know whether the query is good or if you have a better solution.

回答1:

that looks like the correct great circle distance query.

what are you concerned with wrt accuracy?

回答2:

if you want calculate distance from to point or find nearly place to one pointin mysql, you can use "MySQL Spatial Functions", but it is enable in MySQL 5.6. for more information you can read this article:

https://www.percona.com/blog/2013/10/21/using-the-new-mysql-spatial-functions-5-6-for-geo-enabled-applications/

or this PDF:

http://www.arubin.org/files/geo_search.pdf

来源：https://stackoverflow.com/questions/6574599/mysql-within-distance-query

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