Searching a MySQL database for values serving the input lat/long

问题

This question is different from regular mysql lat/long, radius based data fetching

I want to search a mysql database table which contains following columns for example-

ID  Items   lat       long      serving_radius(in km)

1   Item1  26.120888  85.364723    2
2   Item2  26.120888  85.364723    5
3   Item3  25.859800  85.786598    4
4   Item4  26.594900  85.504799    8

Now if a user has lat/long (29.941095/77.812424) wants to know which of these items can be served at his location. Then how i will fetch the result using php & mysql.

回答1:

Is "serving_radius" already stored in your table ? What you can do is fetch distance and check if its under serving_radius

SELECT serving_radius, 
(6371 * acos(cos(radians(" . $userLatitude . ")) * cos(radians(`latitude`)) * cos(radians(`longitude`) - radians(" . $userLongitude . ")) + sin(radians(" . $userLatitude . ")) * sin(radians(`latitude`)))) as distance 
having distance < serving_radius

回答2:

I guess the SQL you are looking for is this one:

SELECT id, items, lat, long, serving_radius
FROM table 
WHERE lat = 29.941095 
AND long = 77.812424;

In your PHP code, you should use a DB driver (I recommend you PDO) in order to connect to the DB and execute the query.

There are plenty of tutorials about how to using PDO (creating the connection, selecting, inserting, etc).

I just found this tutorial which could help you: https://parzibyte.me/blog/en/2019/10/14/php-mysql-tutorial-using-pdo/

Edit: Not sure if you mean about how to build a query with those exact lat and long values or closer to them. If so, you can take a look at https://gis.stackexchange.com/questions/31628/find-points-within-a-distance-using-mysql

回答3:

This question seems to be similar to MySQL - Find points within radius from database

Find the radius from your serving_radius and lat/lon at the database.
use the function MBRContains to find the polygon that contains the user's point.

    SELECT
        *
    FROM 
        items
    WHERE
        MBRContains(
            GeomFromText('Polygon((0 0,0 100,100 100,100 0,0 0))'),
            GeomFromText('Point(77.812424 29.941095)')) = 1;

hope it helps

回答4:

I think your problem is tougher than the traditional problem due to the radius being variable.

See http://mysql.rjweb.org/doc.php/find_nearest_in_mysql for discussion.

That lists 5 ways to "find the nearest X". The simplest, but slowest, is check every item for its distance. All the rest are faster because of using a "bounding-box" to limit how many items need to be checked. However, the coding gets complex.

A bounding-box, in your case, could be limited to the maximum radius in the table. Your sample data show radii of up to 8, so building a square of side 2*8 around the starting point would let you feed into the various techniques I describe.

The simplest involves INDEX(lat, lng), INDEX(lng, lat) to let the Optimizer pick which is better. The advantage is that it checks only items in a 16-wide band of latitude (or longitude), not the entire globe. The disadvantage is that it does not do much to optimize the other direction.

I suggest you use that technique as a first cut. If you need more performance then read further in my document and, optimally, come back for more help,

The techniques discussed there also allow for limiting the number of returned values.

来源：https://stackoverflow.com/questions/61359793/searching-a-mysql-database-for-values-serving-the-input-lat-long

标签

php

mysql

geolocation

latitude-longitude