PHP删除数据库数据

<?php
  $code = $_GET["code"];
  $db = new MySQLi("localhost","root","123456","study");
  !mysqli_connect_error() or die("连接失败！");
  $sql = "delete from `员工信息` where 工号 ="{$code}"";
  $r = $db->query($sql);
  if($r)
  {
      header("location:work.php");
 //echo "<script>alert("删除成功")</script>";
  }
  else
  {
      echo "删除失败！";
  }
?>