Return count of rows matching distance query based on lat/lng in MYSQL?

Question

I'm using this query to find providers within a certain distance, I know it's not an ideal way to do this and it only returns a semi-accurate distance as the crow flies, but the distance is going to have to be calculated far too many times to use any third party API's.

SELECT ( 3959 * acos( cos( radians('28.65') ) * cos( radians( lat ) ) * cos( radians( lon ) - radians('-81.21') ) + sin( radians('28.65') ) * sin( radians( lat ) ) ) ) AS distance FROM providers HAVING distance < 10

That works fine and returns all providers within 10 miles, however I want to return a count of the results, something like this:

SELECT COUNT(providers.id) AS rowcount, ( 3959 * acos( cos( radians('28.65') ) * cos( radians( lat ) ) * cos( radians( lon ) - radians('-81.21') ) + sin( radians('28.65') ) * sin( radians( lat ) ) ) ) AS distance FROM providers HAVING distance < 10

That, unfortunately, does not work.

Is there any other way to do this within the query or do I have to count the rows afterwards with PHP?

Answer 1

You can use a subquery:

SELECT COUNT(*) FROM (
    SELECT (3959 * ACOS(COS(RADIANS('28.65')) * COS(RADIANS(`lat`)) * COS(RADIANS(`lon`) - RADIANS('-81.21')) + SIN(RADIANS('28.65')) * SIN(RADIANS(lat)))) AS distance
    FROM providers
    HAVING distance < 10
)

The inner query is your original one, and then the outer query counts the results.

As mentioned in comments, you should alter your database to use MySQL's spatial data types , which will allow you to do this automatically and with indexes to make it faster.