ช่วยดูให้ทีคับ คำสั่ง update("orderid","OrderID=OrderID+1","where 1") ไม่ update ข้อมูล

//============ กรณีเลือกทำการ บันทึกข้อมุลสั่งซื้อ
if($_POST["action"]=="add")
{
// อ่าน OrderID
$strResultOrderID=select("orderid","where 1");
$strOrderID="ORDER-".substr("000000000$strResultOrderID[OrderID]", -6);

//อ่าน MemberID
$strMemberID=select("member","where 1 and Email='".$_SESSION["strEmail"]."'");
{
if(strMemberID)
$sql2 = "update member set buy=buy+$strTotal";
			$dbquery = mysql_query($sql2);

}

// Insert Order
$sql = "insert into cusorder (OrderNo,MemberID,Email,Total,Date) Values ('$strOrderID','$strMemberID[MemberID]','".$_SESSION["strEmail"]."','$_POST[txtTotal]','".date("Y-m-d")."')";
$dbquery = mysql_query($sql);
								  
// Insert Detail

for($i=0;$i<=count($_SESSION["strProductID"]);$i++)
{
	$result=select("product","where 1=1 and ProductID='".$_SESSION["strProductID"]["$i"]."' ");
	if($result)
	{
			$Proid=$_SESSION["strProductID"]["$i"];
			$Quanlity=$_SESSION["strQuanlity"]["$i"];
			$Proid2=$_SESSION["strEmail"];
			$sql = "update product set count=count+$Quanlity where ProductID='$Proid'";
			$dbquery = mysql_query($sql);
			
			$sql = "insert into order_detail (OrderNo,ProductID,Quanlity) Values ('$strOrderID','".$_SESSION["strProductID"]["$i"]."','".$_SESSION["strQuanlity"]["$i"]."')";
			$dbquery = mysql_query($sql);
			
		
			
	}
}

// Update Order ตัวต่อไปให้เป็น 1
update("orderid","OrderID=OrderID+1","where 1");

	$_SESSION["strP"]="";
	$_SESSION["strProductID"]="";
	$_SESSION["strQuanlity"]="";
	session_write_close();