mysql_query() fout

<?php
include("inc_connect_mysql.php");
if (!empty($_POST)){

	$email = $_POST["email"];
	$wachtwoord = $_POST["wachtwoord"];
	$query = "SELECT * from users WHERE email='$email';";
	$result = mysql_query($db, $query) or die (mysql_error());
	if (mysql_num_rows($result) > 0) { // ........
}

<?php
include("inc_connect_mysql.php");
if (!empty($_POST)){
 
	$email = $_POST["email"];
	$wachtwoord = $_POST["wachtwoord"];
	$query = "SELECT * from users WHERE email='$email';";
	$result = mysql_query($db, $query) or die (mysql_error());
	if (mysql_num_rows($result) > 0) { // ........
}

<?php
include_once 'inc_connect_mysql.php';
if($_SERVER['REQUEST_METHOD'] == 'POST')
	{
	$sQuery = "SELECT * FROM `users` WHERE `email` = '".addslashes($_POST['email'])."'";
	if(!$rRes = mysql_query($sQuery))
		{ echo 'Gegevens opvragen is niet gelukt.'; }
	else
		{
		if(mysql_num_rows($rRes) > 0)
			{
			//...
			}
		else
			{
			}
		}
	}
?>

<?php
include_once 'inc_connect_mysql.php';
if($_SERVER['REQUEST_METHOD'] == 'POST')
	{
	$sQuery = "SELECT * FROM `users` WHERE `email` = '".addslashes($_POST['email'])."'";
	if(!$rRes = mysql_query($sQuery))
		{ echo 'Gegevens opvragen is niet gelukt.'; }
	else
		{
		if(mysql_num_rows($rRes) > 0)
			{
			//...
			}
		else
			{
			}
		}
	}
?>