ปัญหาการทำระบบ login ไม่ได้ เกี่ยวกับ mysql_fetch_row ของ php mysql

<?php
  session_start();
  include("../connectdb.php");
   echo '<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />';
  $sql = "select * from tbadmin where admin_username = '".$_POST['txtUsername']."' and admin_password = '".$_POST['txtPassword']."'";
  $result = mysql_query($sql);
  $num = mysql_num_rows($result);
  if($num > 0)
  {
  	$rs = mysql_fetch_array($result);
	$_SESSION['admin_login'] = $rs["admin_id"];
	echo "<script>  window.location='product.php';</script>";
  }
  else 
  {
  	echo "<script> alert('ชื่อหรือรหัสผ่านไม่ถูกต้องค่ะ'); window.location='../index.php';</script>";
  }
?>

<?
include("ConnectDB.php");
$user=$_POST['user'];
$pw=$_POST['pw']; 
	$sql = "SELECT * FROM staff WHERE Username = '".trim($_POST['user'])."' 
	and Password = '".trim($_POST['pw'])."'";
	$DBquery=mysql_db_query($DBName, $sql) or die(mysql_error() . "<br/>" . $sql);
	$num_rows = mysql_fetch_row($DBquery);
	if($num_rows == 1)
	{
			echo " ข้อมูลถูกต้อง" ;
			}
			else {
			echo "ข้อมูลผิด";
	}
?> 

<?
	session_start();
	mysql_connect("localhost","root","root");
	mysql_select_db("mydatabase");
	$strSQL = "SELECT * FROM member WHERE Username = '".trim($_POST['txtUsername'])."' 
	and Password = '".trim($_POST['txtPassword'])."'";
	$objQuery = mysql_query($strSQL);
	$objResult = mysql_fetch_array($objQuery);
	if(!$objResult)
	{
			echo "Username and Password Incorrect!";
	}
	else
	{
			$_SESSION["UserID"] = $objResult["UserID"];
			$_SESSION["Status"] = $objResult["Status"];

			session_write_close();
			
			if($objResult["Status"] == "ADMIN")
			{
				header("location:admin_page.php");
			}
			else
			{
				header("location:user_page.php");
			}
	}
	mysql_close();
?>

<?
include("ConnectDB.php");
$user=$_POST['user'];
$pw=$_POST['pw']; 
	$sql = "SELECT * FROM staff WHERE Username = '".trim($_POST['user'])."' 
	and Password = '".trim($_POST['pw'])."'";
	$DBquery=mysql_db_query($DBName, $sql) or die(mysql_error() . "<br/>" . $sql);
	$num_rows = mysql_num_rows($DBquery);   // เปลี่ยนตรงนี้ดูยังครับ
	if($num_rows == 1)
	{
			echo " ข้อมูลถูกต้อง" ;
			}
			else {
			echo "ข้อมูลผิด";
	}
?> 

$sql = "select * from staff where Username = '".$_POST['username']."' and Password = '".$_POST['password']."' ";