如何在php中基于下拉列表检索数据

我的代码有问题。。我对php一无所知，所以如果有人能帮助我，我真的很感激："（..我正试图根据所选的下拉列表值显示数据库中的数据。我的数据库表中目前有三个数据。然而，我的输出中只显示了一个。我不知道我的代码出了什么问题。有人能帮我吗？.

这是我的代码部门列表.php

Choose Department : 
     <form action="" method="POST">
     <select name="department">
        <option value="" selected="selected">-- Choose department --</option>
       <option value="Information System Department">Information System Department</option>
      <option value="Finance">Finance</option>
      <option value="HR and Administration">HR and Administration</option>
      <option value="Security">Security</option>
        </select>
     <input type="submit" value="Submit" />
    </form>
    </br>
    <table border="1" id="table">
     <tr><th bgcolor="#00CCCC">Department</th>
     <th bgcolor="#00CCCC">Locaion</th>
     <th bgcolor="#00CCCC">Serial Number</th>
     <th bgcolor="#00CCCC">Description of asset</th>
   </tr>
        <?php 
        mysql_connect('localhost','root',"") or die('Error1 '.mysql_error());
        mysql_select_db("ams") or die('error2'.mysql_error());

          if($_SERVER['REQUEST_METHOD'] =='POST')
     { $dep=$_POST['department'];
         $query="SELECT * FROM asset WHERE department= '" . $dep . "'";
         $run=mysql_query($query);
         $numrow = mysql_num_rows($run);

         $row=mysql_fetch_array($run, MYSQLI_ASSOC);
        echo "<tr><td bgcolor='#00FFCC'>".$row['department']."</td><td bgcolor='#00FFCC'>".$row['location']."</td><td bgcolor='#00FFCC'>".$row['serialno']."</td><td bgcolor='#00FFCC'>".$row['desc']."</td></tr>";
    }
    }
    ?>
    </table>