protected function appendPart($part, $sql, $bind = false) 
	{
		if (!is_array($sql)) $sql = [$sql];
		
		if (!$this->parts[$part]) 
		{
			$this->parts[$part] = $sql;
		}
		else
		{
			$this->parts[$part] = array_merge($this->parts[$part], $sql);
		}
		
		return $this->appendBind($part, $bind);
	}