ไม่รู้ว่าผิดตรงไหน ถึงไม่ INSERT ข้อมูลให้ ขึ้นว่า Cannot Add Database

<?
@session_start();
ob_start();
$useradmin = $_SESSION["useradmin"];
if(empty($useradmin)) 
{
echo "<script>alert('หน้านี้จำกัดเฉพาะ Admin เท่านั้น');history.back();</script>";
exit();
}
require_once "../include/tdate.php";
require_once "../include/connect.php";
require_once "../include/connectdb.php";

						  $sql="select * from useradmin where useradmin='$useradmin'";
						  $db_query=mysql_db_query($db,$sql);
						  $result=mysql_fetch_array($db_query);
						  $id=$result[id];
						  $adminname=$result[name];
						  $user_admin=$result[useradmin];
						  $pass_admin=$result[passadmin];
$select_checkcourse="select * from course where course_code = '$_POST[course_code]'";
$query_select3=mysql_query($select_checkcourse);
$num_prdtype=mysql_num_rows($query_select3);

if($num_prdtype > 0){
echo "<script>alert('รหัสรายวิชานี้ถูกใช้ไปแล้ว!');history.back();</script>";
}else{
mysql_query("INSERT INTO course (course_code,course_name, credit,term,course_year,course_room,course_day,time_star,course_stop ) 
values('','$_POST[course_code]','$_POST[course_name]' ,'$_POST[credit]','$_POST[term]','$_POST[course_year]', '$_POST[course_room]','$_POST[course_day]','$_POST[time_star]', '$_POST[course_stop]')")or die ("Cannot Add Database");
}
?>