您好，我有这段代码，它运行得很好，但我认为它使用了大量服务器资源，因为要对存储在组中的每个用户id执行数据库查询，有什么方法可以解决这个问题吗？还有，我如何使用准备好的语句？

$event_start_date = date(\'d-m-Y\', strtotime($new_start_date));
    $notification = "Nuovo evento <span class=\'text-warning\'><strong>$event_title</strong></span> inizia il $event_start_date";
    $notification_status = "0";
    $notification_category= "events";


    $sql = "SELECT user_join_id FROM user_group_join WHERE group_join_id=\'$event_group\'";

    $result= mysqli_query($conn,$sql);

    $datas= array();

    if(mysqli_num_rows($result) > 0){

        while($row=mysqli_fetch_array($result, MYSQLI_ASSOC)){

        $datas[]= $row;

        }

    }

    foreach($datas as $data) {

    $id_cliente = $data[\'user_join_id\'];

    $event_notification = mysqli_prepare($conn, "INSERT INTO user_notifications (notification_sent_by, notification_sent_to, notification_message, notification_time, notification_status, notification_category, notification_category_id) VALUES(?,?,?,now(),?,?,?)");
    mysqli_stmt_bind_param($event_notification, \'iisisi\', $userid, $id_cliente, $notification, $notification_status, $notification_category, $event_id);
    mysqli_stmt_execute($event_notification);
    mysqli_stmt_close($event_notification);

    }