php - How to get places with a certain radius

I have a database of activities , each activities could be held on 3 days , each day contains a postal code .

So the database looks like that (+ alot of other fields)

In another database i have a Geo Location info (postal code , lat , long)

Now users can enter there postal code and a radius and activities in that radius will appear.

Question :

1 - What is the best way to accomplish that ?

Solution in mind

Make a view of all possible postal codes from the activities and join it on the Geo table to get their Lat/Lng

then when a user search for a postal code , get the Lat/Lng and do the mathematical equation to get all postal codes near that point .

But i don't think in term of performance this is a good way since i will have to apply the query on 3000+ activities

Codes found for distance

• Finding locations nearby with MySQL (Haversine Formula)

  
  
  
  

  SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) ) * cos( radians( lng ) - radians(-122) ) + sin( radians(37) ) * sin( radians( lat ) ) ) ) AS distance
  FROM markers
  HAVING distance < 25
  ORDER BY distance LIMIT 0 , 20;

What do you guys think ?

Answer

I was wrong in term of performance , the query took less than 0,5 second to calculate the distance on the 3000+ activities .