radius search with point data in mysql
SELECT id, ( 6371 * ACOS( COS( RADIANS( db_latitude ) ) * COS( RADIANS( $user_latitude ) ) * COS( RADIANS( $user_longitude ) - RADIANS( db_longitude ) ) + SIN( RADIANS( db_latitude ) ) * SIN( RADIANS( $user_latitude) ) ) ) AS distance FROM the_table HAVING distance <= $the_radius ORDER BY distance ASC"