/**
	 * Builds the GROUP BY part
	 * 
	 * @return string
	 */
	protected function _buildGroupByPart()
	{
		$sql = '';
		
		if (count($this->_info['groupBy'])) {
			$sql = ' GROUP BY ' . implode(', ', $this->_info['groupBy']);
			if (count($this->_info['having'])) {
				$sql .= ' HAVING ' . $this->_query->_concatConditions($this->_info['having']);
			}
		}
		
		return $sql;
	}