public function on($column1, $op, $column2)
	{
		if ($this->active_join === null)
		{
			throw new \Peyote\Exception("You need to start a join before calling \Peyote\Join::on()");
		}

		list($table, $type) = $this->active_join;
		$this->active_join = null;
		$this->joins[] = array("ON", $table, $type, $column1, $op, $column2);
		return $this;
	}