How does an application perform a proximity search? For example, a user types in a postal code, then the application lists all the businesses within 20 miles ordered by proximity.
I want to build something like that in PHP and MySQL. Is this approach correct?
- Get the addresses for locations I’m interested in and store in my database
- Geocode all the addresses with Google’s geocoding service
- Write a database query that includes Haversine formula to do the proximity search and ordering
Is this OK? In step 3, I’m going to calculate the proximity for every query. Is it better to have a PROXIMITY table that lists the distance between every business and a few reference locations?
If there are enough records for speed to matter, here’s a way to index them ahead of time.
Define a grid of bins about 20 miles on a side. Store the bin number with each store’s record. At search time, compute the numbers of all bins that intersect a 20-mile radius from your search point. Then retrieve all stores in any of those bins, and proceed as before.