在mySQLi中查询经度和纬度

Question

我正在尝试在特定数量的英里范围内查询更大的城市半径。例如，该查询基于搜索距离波兰Siemianowice Slaskie 500英里范围内的用户的用户。

城市表结构

city_id_PK  int(11)
region_id   varchar(2)
city_name   varchar(100)   
latitude    float(10,6)
longitude   float(10,6)

mysqli查询

SELECT DISTINCT
  3959 * 2 * ASIN(
    SQRT(
      POWER(
        SIN(
          (50.299999 - abs(b.latitude)) * pi() / 180 / 2
        ),
        2
      )
      +
      COS(50.299999 * pi()/180)
      * COS(abs(b.latitude) * pi() / 180)
      * POWER(
       SIN(
         (19.033333 - b.longitude) * pi() / 180 / 2
       ),
       2
      )
    )
 ) AS distance 
FROM
  users a,
  city b 
WHERE
  a.user_name != 'myusername'
  AND b.city_name = 'siemianowice slaskie'
  AND a.region_id = b.region_id
HAVING
  distance <= 500
ORDER BY
  distance,
  RAND()

距离总是太小。

结果

+-----------------------+
|        distance       |   
+-----------------------+ 
|0.000018115605488822287|
|0.000018115605488822287|
|0.000018115605488822287|
|...                    |
|....                   |