wpdb returns null on pages

I’m trying to access my database through one of my pages and wpdb keeps on returning null. Here’s my code:

<?php
	global $wpdb;
	$table_name = $wpdb->prefix . "mcpd_currency";
	$results = $wpdb->get_var("SELECT code FROM ".$table_name." WHERE currency='Australian Dollars'", ARRAY_A);

var_dump($results);
?>

This works when I use this on my plugin files but not on a page. Does anyone know why this is?