编辑更新记录mysqli

Question

我的代码表示记录已更新，但实际上未在数据库中更新。找不到漏洞。值得正确回显，但编辑和更新时会给出错误的更新。

if( isset($_GET['Edit']) )
{
  //<a href='edit.php?Edit=<?php echo $rows["id"]; ?>'>Edit</a>
  $id = (int)$_GET['Edit'];
  $res= mysqli_query($db  ,"SELECT * FROM a WHERE id=$id");
  $row= mysqli_fetch_array($res);
}

//table columns id tid Treat
if(isset($_POST['submit'])) {
  $id = (int)($_POST['tid']);
  $Treat = (int)($_POST['tname']);
  $sql = "Update a set `Treat`='".$Treat."' where `id`=$id";

  $query = mysqli_query($db  ,$sql);

  if(!$query)
    echo mysqli_error();
  else     
    echo "Successfully Updated";
}

<tr>
  <td class="desc" align="right">Treat</td>
  <td class="desc" align="left"><input type="text" name="tname"  value="<?php echo $row['Treat'] ; ?>" class="field text ln" /></td>
</tr>

?>