ช่วยดูทีคับ แก้ 10 กว่ารบแล้ว mysql_fetch_array(): supplied argument is not a valid MySQL result resource

<?
ob_start();
@session_start();
include("connect.php");
$sql = mysql_query("select *from item  where  id_item  = $_GET[id_item]");
$fetch = mysql_fetch_array($sql);
?>
<style type="text/css">
<!--
.style1 {
	color: #FFFFFF;
	font-weight: bold;
}
-->
</style>
        <? if($fetch[num] < $_POST[num]){
echo "<script>
		alert('จำนวน $fetch[name] มีไม่พอกับจำนวนที่ต้องการยืม!');
		window.location='user_page.php';
		</script>";

}else{
$up_equipment =mysql_query("update item set id_item  = num-$_POST[num] where  id_item  = $_POST[id_item] " );	
    $count_equipment =mysql_query("update item set count  = count +1 where  id_item  = $fetch[id_item] " );	
 $result=mysql_query("INSERT INTO borrow  VALUES ('','$_POST[id]','$_POST[id_item]','$_POST[num]','n')");
  header("location:user_page.php");
mysql_close($conn);
}
ob_end_flush();
?>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=windows-874">