A custom MySQL function to calculate the Haversine distance?

Question

I\'m building a \'find my nearest\' script whereby my client has provided me with a list of their locations. After some research, I determined that the way to do this was t

Answer 1

Yes, you can create a stored function for this purpose. Something like this:

DELIMITER //
  DROP FUNCTION IF EXISTS Haversine //
  CREATE FUNCTION Haversine
    ( myLat FLOAT
    , myLong FLOAT
    , db_lat FLOAT
    , db_long FLOAT
    , unit VARCHAR(20)
    )
    RETURNS FLOAT
      DETERMINISTIC
    BEGIN
      DECLARE haver FLOAT ;

      IF unit = 'MILES'                    --- calculations
        SET haver = ...                --- calculations

      RETURN haver ;
    END  //
DELIMITER ;

I don't think it offers any speed gains but it's good for all the other reasons you mention: Readability, reusability, ease of maintenance (imagine you find an error after 2 years and you have to edit the code in a (few) hundred places).