Can't get wpdb->rows_affected to work right

Hi,

I’m trying to figure out how many rows were deleted. rows_affected keeps returning a value of ‘0’, no matter how many rows are deleted:

if(is_numeric($_POST['delete_coupons'])){

		$delete_coupons = $_POST['delete_coupons'];
		$delete_query="
			DELETE
			FROM ".$coupon_table."
			ORDER BY id
			DESC
			LIMIT $delete_coupons
		";
		$wpdb->query($delete_query);
		$rows_deleted=$wpdb->rows_affected;
		if($rows_deleted > 0){
			echo"You just deleted the $rows_deleted most recently created coupons!";
		}else{
			echo"rows_deleted:$rows_deleted <br> There was an error and the coupons could not be deleted.";
		}
	}else{die;}