慢速 sql 选择.两张桌子

搜索 90210 30 英里内的邮政编码时，我的脚本运行速度太慢。即使邮政编码数据库中也没有重复，它也复制了一些，因此是 DISTINCT u.id。除了只选择我需要的列之外，关于如何加快这件事有什么想法吗？

<?php
$zipcode = queryDB("SELECT * FROM zipcodes WHERE zipcode='$location' LIMIT 1", 'a');
$distance = 30;
$sql = "SELECT DISTINCT zipcode, ( 3959 * acos( cos( radians(".$zipcode['lat'].") ) * cos( radians( lat ) ) * cos( radians( lon ) - radians(".$zipcode['lon'].") ) + sin( radians(".$zipcode['lat'].") ) * sin( radians( lat ) ) ) ) AS distance FROM zipcodes HAVING distance <= $distance ORDER BY distance";
$zipcodes = queryDB($sql, 'r');
$sql = '';
while($row = mysqli_fetch_assoc($zipcodes)){
    $sql .= "u.category='$category' AND u.zipcode='".$row['zipcode']."' AND u.zipcode = l.zipcode";
    if($_GET['photos'] == 'y'){ $sql .= " AND photo_1!=''"; }
    $sql .= " OR ";
}
$sql = rtrim($sql, ' OR ');
$profiles = queryDB("SELECT DISTINCT u.id, u.*, l.city, l.state, l.zipcode FROM user_accounts as u, zipcodes as l WHERE $sql ORDER BY date_added DESC", 'r');
while($row = mysqli_fetch_assoc($profiles)){
//this is where i display the profile information
} ?>

更新：最大的问题是没有在我的user_accounts选择中使用联接。这是我更新的 sql 查询。

    $sql = '';
$zipcodes = new ZipCodesRange($location, $distance);
foreach ($zipcodes->zipCodes as $zipcode){
    $sql .= "(u.category='$category' AND u.zipcode='".$zipcode['ZIPCODE']."'";
    if($_GET['photos'] == 'y'){ $sql .= " AND photo_1!=''"; }
    $sql .= ") OR ";
}
$sql = rtrim($sql, ') OR ');
$sql .= ")";

$profiles = queryDB("SELECT u.id, u.photo_1, u.name, u.business, u.date_added, l.city, l.state, l.zipcode FROM user_accounts as u INNER JOIN zipcodes as l ON u.zipcode = l.zipcode WHERE $sql ORDER BY date_added DESC", 'r');