PHP insert ข้อมูลหลาย record จะเช็คข้อมูลซ้ำได้อย่างไร

<?php
include("config.inc.php");
$user = $_REQUEST["user"];
$code = $_REQUEST["code"];

$ex= explode("\n", $code);
for($i=0;$i<count($ex);$i++)
{

	$new_id = mysql_result(mysql_query("Select Max(prid)+1 as MaxID from fb_group_id"),0,"MaxID");
            if($new_id==''){ 
                $prid="00001";
            }else{
                $prid=sprintf("%05d",$new_id);
            }

		$sql = "Insert into fb_group_id (prid,group_id,user) VALUES ('$prid','".$ex[$i]."','$user')";
		$query = mysql_query($sql,$connect) or die ("ERROR Query");
}
		echo ("<script>alert('เพิ่ม ID กลุ่มสำเร็จ');window.location='group_id.php';</script>");	
?>