ปรึกษาเรื่อง คิวรี่ข้อมูลในส่วนของการ delete ข้อมูลไม่ได้

<?php
require_once('connection.php');

if (isset($_REQUEST['delete_mac_add'])) {
    $de = $_GET['delete_mac_add'];

    $sql1 = "SELECT * FROM tbl_new_pc WHERE mac_add=$de ;";
    $result1 = $mysqli->query($sql1);
    while ($row = $result1->fetch_array(MYSQLI_ASSOC)) {

    // sql to delete a record
    $sql1 = "DELETE FROM tbl_new_pc WHERE mac_add=$de ;";
    $result1 = $mysqli->query($sql1);

            if (mysqli_query($mysqli, $sql1)) {   
                echo "<script>alert('Delete Data Successfully...'); window.location ='modalmasterpc.php';</script>";
            } else {
                echo "Error: " . $sql1 . "<br>" . mysqli_error($mysqli);
            }
    
            mysqli_close($mysqli);
        }

 }
?>