Как правильно написать SQL запрос?

$art- артикул
$prodtitle- наименование
$price_1- цена1
$price_2- цена2

$glob_files = glob($_SERVER['DOCUMENT_ROOT'] . '/bitrix/admin/upload/offers*.xml');
usort($glob_files, function ($a, $b) {
    return filemtime($a) - filemtime($b);
});
foreach ($glob_files as $xml_name) {
    $xml_data = file_get_contents($xml_name, "SimpleXMLElement");
    $xml = new SimpleXMLElement(mb_substr($xml_data, 0, mb_stripos($xml_data, '</КоммерческаяИнформация>')) . '</КоммерческаяИнформация>');
    if (!empty($xml)) {
        $price_cnt = count($xml->ПакетПредложений->Предложения->Предложение);
        for ($i = 0; $i < $price_cnt; $i++) {
            $price = $xml->ПакетПредложений->Предложения->Предложение[$i];

            if (empty($price->Артикул)) continue;
            $art = (string)$price->Артикул;
			
			$prodtitle = (string)$price->Наименование;
		

            $price_1 = (float)$price->Цены->Цена[0]->ЦенаЗаЕдиницу;
            $price_2 = (float)$price->Цены->Цена[1]->ЦенаЗаЕдиницу;

            if (empty($price_1)) continue;

            $query = $db->prepare("SELECT `virtuemart_product_id` FROM `jos_virtuemart_products` WHERE `product_sku` = :product_sku LIMIT 1");
            $query->execute(array('product_sku' => $art));
            $prod_id = $query->fetchColumn(0);
            if (empty($prod_id)) continue;

            $query = $db->prepare("SELECT * FROM `jos_virtuemart_product_prices` WHERE `virtuemart_product_id` = :virtuemart_product_id LIMIT 1");
            $query->execute(array('virtuemart_product_id' => $prod_id));
            $price_old = $query->fetch(PDO::FETCH_ASSOC);

            // if($price_old['product_price'] <> $price_1) echo $art."\n";

            $query = $db->prepare("UPDATE `jos_virtuemart_product_prices` SET `product_price` = :price_1, `product_override_price` = :price_2  WHERE `virtuemart_product_id` = :virtuemart_product_id LIMIT 1");
            $query->execute(array('price_1' => $price_1, 'price_2' => $price_2, 'virtuemart_product_id' => $prod_id));

            file_put_contents($_SERVER['DOCUMENT_ROOT'] . '/bitrix/admin/logs/' . date('y-m-d') . '.txt', date('H:i:s ' . $art . ' ' . $price_old['product_price'] . ' ' . $price_1 . "\n"), FILE_APPEND);
        }
    }

    rename($xml_name, $_SERVER['DOCUMENT_ROOT'] . '/bitrix/admin/archive/' . str_replace('.xml', date('-y-m-d-h-i-s') . '.xml', basename($xml_name)));
}