Do you calculate the distance between the zip codes in a scripting language (PHP, Perl, ASP, etc) or with an expression in your SQL query?

<?php
// truncate distance table.
$sql= "TRUNCATE TABLE distance"; 
$disResult= mysql_query($sql, $conn) or die("<br>** Unable to truncate distance database table <b>".mysql_error()."</b><br>$sql"); 
$disRows= mysql_affected_rows($conn);

if (!$disResult){ 
echo "<br>** Unable to truncate distance database table. disResults[$disResults], disRows[$disRows]";
exit;
}


// Get latitudinal and longitudinal data from selected zip codes in zipcode table to calculate distance between the base zip code and the selected zip codes.
while ($i < $chrRows) {
$chrZipCode= mysql_result($chrResult,$i,"ZipCode");
$sql= "SELECT * FROM zipcodes WHERE ZipCode = '". $chrZipCode ."'";
$zipResult= mysql_query($sql, $conn)or die("<br>** Unable to query local database table for base zip code data <b>". mysql_error() ."</b><br>$sql"); 
//echo "<br>** zipcodes SQL statment: $sql";

$zipResult_ar= mysql_fetch_assoc($zipResult);
$zipLatitude= $zipResult_ar['Latitude'];
$zipLongitude= $zipResult_ar['Longitude'];

$chrCID= mysql_result($chrResult,$i,"CID");
$chrMercyCode= mysql_result($chrResult,$i,"MercyCode");

// calculate the distance and mercycode restrictions.
$chrDistance= number_format(DistanceCalc($zip1Latitude, $zip1Longitude, $zipLatitude, $zipLongitude, "M"), 2);
$mercyTest= $mercyMask & $chrMercyCode; if ($mercyTest == '00000000000000') $mercyTest = "";
//echo "<br>** [$i -- $chrRows], [$chrDistance -- $miles], mercyTest[$mercyTest] = mercyMask[$mercyMask] & chrMercyCode[$chrMercyCode]";

// store pointer to all charities table records that meet the distance and mercycode restrictions.
if (($chrDistance <= $miles) and ($mercyTest)) {
$sql= "INSERT INTO distance (Miles, CID) VALUES ('$chrDistance', '$chrCID')";
$disResult= mysql_query($sql, $conn)or die("<br>** Unable to insert local database table for distance data <b>". mysql_error() ."</b><br>$sql"); 
$disRows= mysql_affected_rows($conn);

if (!$disResult){
echo "<br>** distance table insert failed. disResults[$disResults], disRows[$disRows]";
exit;
}
}

$i++;
}


// select all records in the distance table and use the CID pointer to get matching business records in the charities table.
$sql= "SELECT * FROM distance ORDER BY Miles ASC";
$disResult= mysql_query($sql, $conn) or die("<br>** Unable to query distance database table <b>".mysql_error()."</b><br>$sql");
$disRows= mysql_num_rows($disResult);
//echo "<br>** distance table base query, $disRows records found.";

if ($disRows < 1){ 
echo "<br>** distance table base query failed.";
}else{
$i= 0;
$sql= "SELECT * FROM charities WHERE ";

// get all records from the charities table that match the distance CID and meet the merctcode restrictions.
while ($i < $disRows) {
$disCID[$i]= mysql_result($disResult,$i,"CID");
$sql = $sql."(CID = '".$disCID[$i]."')";
$i++;

if ($i < $disRows) $sql = $sql." OR ";
}

$sql= $sql." AND (ZipCode <> '')";
$chrResult= mysql_query($sql, $conn) or die("<br>** Unable to query charities database table for zip codes <b>".mysql_error()."</b><br>$sql");
$chrRows= mysql_num_rows($chrResult);
//echo "<br>** distance SQL statment: $sql";
}
?>