ต้องการสุ่มข้อสอบ โดยสุ่มมาแค่ 5 ข้อ เอาแบบสุ่มไม่ซ้ำกันด้วยน่ะครับ ขอ code ด้วยครับ

<?php
include('connect.php');

$sql="select*from qq order by rand() limit 3 ";
$result=mysql_query($sql,$con);
$number=0;
?>
<table align="center" width="780" cellpadding="0" cellspacing="0">
<tr> 
<td><div id="header">ข้อสอบ</div></td>
</tr>
<tr><td>
<div id="maintain"><form action="check_answer.php" method="post">
  <table align="center" width="780" border="1">
   <? 
while($arr=mysql_fetch_array($result)){
	
	$id=$arr['id'];
	$question=$arr['data'];
	$choice1=$arr['ans1'];
	$choice2=$arr['ans2'];
	$choice3=$arr['ans3'];
	$number++;
	$i++;
echo "<tr>
<td>
 $number
</td>
<td> $question</td>
<td> 
<input type='radio' name='select_$id'  value='1'>
$choice1
<input type='radio' name='select_$id'  value='2'>
$choice2
<input type='radio' name='select_$id'  value='3'> 
$choice3
<input type='hidden' name='total_question[]' value='$id'<br>
</td>
</tr>";
}
?>
    <tr>
      <td  colspan="3"><input type="submit" value="click"  /><input type="reset" value="reset" /></td>
    </tr>
    <tr>
      <td></td>
    </tr>
  </table>
  </form>
  </div>
  </td>
  </tr>
  <tr><td>&nbsp;</td></tr>
  </table>

<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<?
$correct=0;
$total=count($total_question);
echo $total."<br>";
include('connect.php');
$sql="select id, ans_true from qq order by id";
$result=mysql_query($sql);
while ($ar=mysql_fetch_array($result)){
$id=$ar['id'];
$answer=$ar['ans_true'];

if (in_array($id, $total_question)){
	
$select="select_".$id;
if (${$select}==$answer) {
$correct++;
}
}
}
echo "ตอบถูก ทั้งหมด $correct <br> คำถามทั้งหมด $total";

?>

<form name="form1" method="post" action="confirm3.php">
<?
$host="localhost";
$username="root";
$password="1234";
$db="database";
$tb="testing";
mysql_connect( $host,$username,$password) or die ("ติดต่อกับฐานข้อมูล Mysql ไม่ได้ ");
mysql_select_db($db) or die("เลือกฐานข้อมูลไม่ได้");
mysql_query("SET character_set_results=tis620");
mysql_query("SET character_set_client=tis620");
mysql_query("SET character_set_connection=tis620");
$sql="Select * From $tb order by id limit 50";
$db_query=mysql_query($sql);
$i=0;
while($result=mysql_fetch_array($db_query))
{
$i++;
?>
<table width="64%" border="0" align="center">
<tr>
<td width="18%"> <div align="left">
<input name="id<?=$i;?>" type="hidden" value="<?=$result["id"];?>">
<?=$result["question"];?>
</div></td>
</tr>
<tr>
  <td><input name="c<?=$i;?>" type="radio" value="1" checked>
    <?=$result["c1"];?></td>
  </tr>
<tr>
  <td><input type="radio" name="c<?=$i;?>" value="2">
    <?=$result["c2"];?></td>
  </tr>
<tr>
  <td><input type="radio" name="c<?=$i;?>" value="3">
    <?=$result["c3"];?></td>
  </tr>
<tr>
  <td><input type="radio" name="c<?=$i;?>" value="4">
    <?=$result["c4"];?>
    <input name="answer<?=$i;?>" type="hidden" value="<?=$result["answer"];?>"></td>
  </tr>
</table><br>
<?
}
mysql_close();
?>
<div align="center"><br>
<input type="hidden" name="line" value="<?=$i;?>">
<input type="submit" name="Submit" value="ตรวจคะแนน">
</div>
</form>

<form name="form1" method="post" action="updateconfirm3.php">
      <div align="center">
        <p><?
$score=0;
for($i=1;$i<=$_POST["line"];$i++)
{
	If($_POST["c$i"] == $_POST["answer$i"])
	{
			$score=$score+1;
	}
}
echo "<p align='center'>คุณทำข้อสอบได้ $score คะแนนจาก 30 ข้อ<br>";

?></p>
        <table width="182" border="0" bgcolor="#0094DE">
          <tr>
            <td width="176"><div align="center"><span class="style16">คลิกยืนยันสถานะผ่านการทดสอบ</span></div></td>
          </tr>
        </table>
          <br>
        <table width="200" border="0">
          <tr>
            <td><div align="center">
              <select name="txtConfirm" id="txtConfirm"  value="<?=$objResult["Sex"];?>">
                <option value="1">ผ่านการทดสอบก่อนเรียนแล้ว</option>
              </select>
            </div></td>
          </tr>
        </table>
              <label>
        <select name="txtScore3" id="txtScore3">
		<option value="<?php echo"$score"; ?>">คุณทำข้อสอบได้ <?php echo"$score"; ?> คะแนน</option>
        </select>
        </label><br>
          <input type="submit" name="Submit" value="ยืนยัน">
      </div>
    </form>

<?
	session_start();
	if($_SESSION['UserID'] == "")
	{
		echo "Please Login!";
		exit();
	}
	mysql_connect("localhost","root","1234");
	mysql_select_db("database");
			mysql_query("SET character_set_results=tis620");
mysql_query("SET character_set_client=tis620");
mysql_query("SET character_set_connection=tis620");
	
	if($_POST["txtPassword"] != $_POST["txtConPassword"])
	{
		echo "ÃËÑʼèÒ¹äÁèµÃ§¡Ñ¹!";
		exit();
	}
	$strSQL = "UPDATE member SET Confirm = '".trim($_POST['txtConfirm'])."',Score3 = '".trim($_POST['txtScore3'])."' WHERE UserID = '".$_SESSION["UserID"]."' ";
	$objQuery = mysql_query($strSQL);
	header ("Location:contentmain.php"); 
		
	

	mysql_close();
?>