public function exists($userid)
	{
		$query = $this->_db->getQuery(true)
			->select('COUNT(userid)')
			->from($this->_db->quoteName($this->_tbl))
			->where($this->_db->quoteName('userid') . ' = ' . $this->_db->quote($userid));
		$this->_db->setQuery($query);

		if (!$result = $this->_db->loadResult())
		{
			$this->setError($this->_db->stderr());

			return false;
		}

		return (boolean) $result;
	}