Select records based zipcode, it's radius, lat

Question

Below is my company table with it's postalcode, lat, lon and the radius in kilometers where each company is able to provide his services.

id  company_name   city                 postalcode  radiu   latitude       longitude
 1  A              Drogteropslagen      7705 PA     10      52.61666700    6.50000000
 2  B              Coevorden            7740 AA     15      52.66666700    6.75000000
 3  C              Emmen                7812 TN     5       52.78333300    6.9000000
 4  D              Emmer-Compascuum     7881 PZ     25      52.81666700    7.05000000
 5  E              Nieuw-Dordrecht      7885 AA     60      52.75000000    6.96666700

I would like to select the companies which a particular postalcode e.g. 7813 AB lives within their postalcode + the radius, even this postalcode 7813 AB is not exact the same as that of a company. how to write a sql query to select those companies?

Answer 1

You can use spatial datatypes for longitude and latitude (or convert them) and then calculate the difference with st_difference, see https://dev.mysql.com/doc/refman/5.7/en/spatial-operator-functions.html#function_st-difference

Example:

SELECT st_distance(POINT(50.0, 8.0), POINT(latitude, longitude)) FROM company;

The distance is, however, a approximation and works best for small distances. With longer distances the calculation error increases due to the fact, that MySQL only calculates planar coordinates (Euclidean geometry).

Answer 2

You will need to convert the input post code to long/lat coordinates.

There are two ways to do this; the most performant way is to import a table with post code and long/lat coordinates. You can find a dataset here for the Netherlands.

The alternative is to use a geocoding API; there are several available; Google is your friend. This can be a performance problem (if you have thousands of customers all submitting post codes at the same time), and may require licensing from the API provider.

Once you have the long/lat for your input post code, you can use geo-spatial logic in MySQL to calculate what's in the radius.

Answer 3

SELECT t1.company_name, t2.company_name,
    (6371 * acos(cos(radians(t1.lat1)) * cos(radians(t2.lat2)) 
    * cos(radians(t2.lng2) - radians(t1.lng1)) + sin(radians(t1.lat1)) * sin(radians(t2.lat2)))) AS distance,
    t1.radius
FROM
(
    SELECT company_name, latitude AS lat1, longitude AS lng1,
        radius
    FROM company
    WHERE postalcode = '7813 AB'
) t1
CROSS JOIN
(
    SELECT company_name, latitude AS lat2, longitude AS lng2
    FROM company
) t2
HAVING distance < t1.radius AND t1.company_name != t2.company_name