【求教】PHP如何验证MySQL数据库update语句是否成功

if($_GET['areas-change']){
$name = $_GET['name'];
$areas = $_GET['areas'];
$sql="update txl set areas='$areas' where name='$name'";
$update = $conn->query($sql);
//echo $update;
$ud = mysqli_affected_rows();
echo $ud;
}