Question

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how to do location based search
Getting similar longitude and latitude from database

I have a dating PHP application working with MySQL database where users enter their location and based on it, other profiles are shown.

Structure of table cities:

int id PK
int country_id FK
varchar(50) name
float longitude
float latitude

Example entry in table:

1 | 1 | New York | 23.20323 | 12.32356

And I want to select all cities which have longitude and latitude less then 23.20323 + 50 km, more then 23.20323 – 50km respectively.

The issue here is not a SQL syntax, but the actual radius calculation.

Answer 1

This should be what you’re after.

//Get your base city location e.g. New York
$base_lat = 12.32356;
$base_lng = 23.20323;

//Get target distance in miles
$target_distance = 31; //50km is approx 31 miles

//Select all cities that are closer than 50km (31 miles)
SELECT id, ( 3959 * acos( cos( radians('.$base_lat.') ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians('.$base_lng.') ) + sin( radians('.$base_lat.') ) * sin( radians( latitude ) ) ) ) AS distance
FROM cities
WHERE latitude IS NOT NULL
AND longitude IS NOT NULL
HAVING distance < $target_distance
ORDER BY distance ASC

//Select all cities that are further than 50km (31 miles)
SELECT id, ( 3959 * acos( cos( radians('.$base_lat.') ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians('.$base_lng.') ) + sin( radians('.$base_lat.') ) * sin( radians( latitude ) ) ) ) AS distance
FROM cities
WHERE latitude IS NOT NULL
AND longitude IS NOT NULL
HAVING distance > $target_distance
ORDER BY distance ASC