Question

I have a working PHP function that takes in latitude/longitude coordinates and a distance in miles, then tests row by row in a MySQL table of zip codes/lat-lon pairs (40,000+ rows) whether each zip code/lat-lon row falls within the specified distance or not.

I know that this method is terribly inefficient and I would like to do all of the trigonometry and distance calculation in the SQL query rather than with PHP. Can anyone help me out here? I feel like I’ve tried everything but I just can’t get the SQL query correct. Any help would be greatly appreciated!

Existing PHP function:

function getZips($lat, $lon, $radius)
{   

//MySQL bit
$zipQuery = mysql_query("SELECT * FROM zip_codes");
while ($row = mysql_fetch_assoc($zipQuery))
{

    $lat2 = $row['latitude'];
    $lon2 = $row['longitude'];

    $distance = (3958*3.1415926*sqrt(($lat2-$lat)*($lat2-$lat) + cos($lat2/57.29578)*cos($lat/57.29578)*($lon2-$lon)*($lon2-$lon))/180);

    if ($distance <= $radius)
    {
        $zip = $row['zip'];
        echo "Zip in range: <b>" .$zip . "</b><br>";
    }

}

}

Answer 1

SELECT zipcode, ( 3959 * acos( cos( radians( {$coords['latitude']} ) ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians( {$coords['longitude']} ) ) + sin( radians( {$coords['latitude']} ) ) * sin( radians( latitude ) ) ) ) AS distance FROM logic_zipcodes HAVING distance <= {$radius} ORDER BY distance

can’t remember where I got this originaly, but I have been using it for a long time. Here is my function:

function zipsearch($start, $rad) {
// ITITIAL POINT
$result = mysql_query("SELECT latitude,longitude FROM logic_zipcodes WHERE zipcode='" . $start . "'");
while($row = mysql_fetch_array($result)) {
    $coords = array('latitude' => $row['latitude'], 'longitude' => $row['longitude']);
}
//RADIUS
$radius = $rad;
// SQL FOR MILES
$sql = "SELECT zipcode, ( 3959 * acos( cos( radians( {$coords['latitude']} ) ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians( {$coords['longitude']} ) ) + sin( radians( {$coords['latitude']} ) ) * sin( radians( latitude ) ) ) ) AS distance FROM logic_zipcodes HAVING distance <= {$radius} ORDER BY distance";

// OUTPUT THE ZIPCODES AND DISTANCES
$query = mysql_query($sql);
$zips = array();
while($row = mysql_fetch_assoc($query)) {
    $zips[] = $row['zipcode'];
}
return $zips;
}
 function getZips($zip, $rad) {
$zipcode = qt($zip);
$andstatement = implode("','", zipsearch($zipcode, $rad));
return "AND zipcode in('" . $andstatement . "')";
 }