ถามเรื่อง Dropdown lits หน่อยครับ + JAVA นิดหน่อย ช่วยหน่อยครับ พี่ๆ

<script type="text/javascript">
function showUser(str)
{
if (str=="")
  {
  document.getElementById("txtHint").innerHTML="5555";
  return;
  } 
if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("select").innerHTML=xmlhttp.responseText;
    }
  }
xmlhttp.open("GET","select.php?q="+str,true);
xmlhttp.send();
}
</script>
							<img src="img/labelsearch.png" width="160" style="padding-top:15px;"/>
<script type="text/javascript" src="js/form-validation.js"></script>

							<form id="contactForm" action="#" method="post">
								<fieldset>
									<div>
										<label>ชนิดของรถ</label>
<select name="users" onChange="showUser(this.value)" style="width:160px;">
	<option value="">-- SELECT --</option>
	<?php 
        $sql = mysql_query("SELECT * FROM car_type WHERE type_level = '1'");
        while($rs = mysql_fetch_array($sql)){
    ?>
    <option value="<?=$rs['type_id'];?>"><?=$rs['type_name'];?></option>
    <?php } ?>
</select>
</div>
<div>
<label>ยี่ห้อรถ</label>
<select id="select" name="select" style="width:160px;">
	<option value="">-- SELECT --</option>
</select>
</form>
</div>
<div>
<label>รุ่นของรถ</label>
<select name="select" id="select" width="250" style="width:160px">
<option>--SELECT--</option>
</div>

<?php
$q=$_GET["q"];
require_once('config/class.mysql.php');
$db = new __DATABASE();
$db->connectdb();
$sql=mysql_query("SELECT * FROM car_type WHERE type_id LIKE '$q%' AND type_level = '2'");
?>
<select id="select" name="select">
<?php 
	while($rs=mysql_fetch_array($sql)){
?>
	<option value="<?=$rs['type_id'];?>"><?=$rs['type_name'];?></option>
<?php }?>
</select>