Close. You need another INNER JOIN and should escape all your variables using $wpdb->prepare. I’ve also included a more efficient Haversine formula (source) to calculate the radius. If you use kilometers, then change the $earth_radius to 6371. Also, a great way to debug is to echo the sql and paste it into phpMyAdmin (or whatever … Read more
There’s Geo Data Store by our own man, @Brady. It does a perfect job in one of my installations. It uses a custom table, that stores only ID, meta ID, lat and lng information, so your queries stay quick and brief, even when your database starts scaling. It got a 5 star rating from my … Read more
What precision do you need? if it’s a state/national wide search maybe you could do a lat-lon to zip lookup and have precomputed distance from zip area to zip area of the restaurant. If you need accurate distances that won’t be a good option. You should look into a Geohash solution, in the Wikipedia article … Read more
I would modify the answer from gabrielk and the linked blog post by using database indexes and minimizing the number of actual distance calculations. If you know the coordinates of the user and you know the maximum distance (say 10km), you can draw a bounding box that is 20km by 20km with the current location … Read more