Unknown column 'Hardware' in 'where clause'

	<?
	$query = "SELECT * FROM i_artikels";
	$sql = mysql_query($query);
	$new_query = "SELECT * FROM i_cats";
	$new_sql = mysql_query($new_query) or die(mysql_error());
	
	if(mysql_num_rows($sql) == 0) {
		echo "Geen artikels gevonden!";
	}
	else
	{
		while($bekijk=mysql_fetch_assoc($new_sql)){
	?>
	<b><?=$bekijk['cat']; ?></b><br>
	<?
	$a = "SELECT * FROM i_artikels WHERE cat = ".$bekijk["cat"]."";
	$b = mysql_query($a) or die(mysql_error());
	
	if(mysql_num_rows($b) == 0) {
		echo "Geen artikels gevonden in deze categorie.";
	}
	else
	{
	while($show=mysql_fetch_assoc($b)){
		?><a href="artikel.php?id=<?=$show['id']; ?>"><?=$show['titel']; ?></a><?
	}
	}
	}
	}
	?>

<?
	$query = "SELECT * FROM i_artikels";
	$sql = mysql_query($query);
	$new_query = "SELECT * FROM i_cats";
	$new_sql = mysql_query($new_query) or die(mysql_error());
 
	if(mysql_num_rows($sql) == 0) {
		echo "Geen artikels gevonden!";
	}
	else
	{
		while($bekijk=mysql_fetch_assoc($new_sql)){
	?>
	<b><?=$bekijk['cat']; ?></b><br>
	<?
	$a = "SELECT * FROM i_artikels WHERE cat = ".$bekijk["cat"]."";
	$b = mysql_query($a) or die(mysql_error());
 
	if(mysql_num_rows($b) == 0) {
		echo "Geen artikels gevonden in deze categorie.";
	}
	else
	{
	while($show=mysql_fetch_assoc($b)){
		?><a href="artikel.php?id=<?=$show['id']; ?>"><?=$show['titel']; ?></a><?
	}
	}
	}
	}
	?>