ช่วยด้วยครับ Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result resource in

<?
include("config.php");
@session_start();
session_register("ses_Pur_Pro_id");
session_register("ses_Pur_Pro_name");
session_register("ses_Pur_Pro_stro");
session_register("ses_Pur_Pro_unit");
session_register("ses_Pur_Pro_unit_wait");
session_register("ses_Pur_Pro_price");
session_register("ses_Pur_amount");
session_register("ses_Pur_total_per_unit");
session_register("ses_Pur_vat");
session_register("ses_Pur_price_vat");
session_register("ses_Pur_price_total");
session_register("ses_vat");
session_register("purchase_total");
session_register("purchase_vat");
session_register("purchase_net");
	if(!session_is_registered("ses_Pur_Pro_id")){
	$ses_Pur_Pro_id=array();
	}
if(isset($_POST[submit])){
$sql_config="SELECT * FROM config WHERE con_id=1";
$result_config=mysql_query($sql_config);
$data_config=mysql_fetch_array($result_config);
	for($i=0;$i<count($inChk);$i++){
	$chk_array=in_array($inChk[$i],$ses_Pur_Pro_id);
		if($chk_array==false && isset($inChk[$i])){
		$sql="SELECT * FROM books WHERE book_id=$inChk[$i]";
		$result=mysql_query($sql);
		$data=mysql_fetch_array($result);  // ตอนรันผิดตรงบรรทัดนี้ครับ 
			$ses_Pur_Pro_id[]=$data[book_id];
			$ses_Pur_Pro_name[]=$data[book_name];
			$ses_Pur_Pro_stro[]=$data[Int_num];
			$ses_Pur_Pro_unit[]=$data[Point_order];
			$ses_Pur_Pro_unit_wait[]=$data[Int_order];
			$ses_Pur_Pro_price[]=$data[Book_price];
			$ses_Pur_amount[]=1;
			$ses_vat[]=$data_config[con_vat];
			$ses_Pur_vat[]=$data[Pro_cost]*$data_config[con_vat];
			}//¨ºif Check array
		}//¨ºfor
}//¨ºif submit
echo "<meta http-equiv=refresh content=0;url=book_order.php />";
?>