protected function _fieldsQuote($alias, $field) {
		list($open, $close) = $this->_quotes;
		$aliasing = preg_split("/\s+as\s+/i", $field);

		if (isset($aliasing[1])) {
			list($aliasname, $fieldname) = $this->_splitFieldname($aliasing[0]);
			$alias = $aliasname ? : $alias;
			return "{$open}{$alias}{$close}.{$open}{$fieldname}{$close} as {$aliasing[1]}";
		} elseif ($alias) {
			return "{$open}{$alias}{$close}.{$open}{$field}{$close}";
		} else {
			return "{$open}{$field}{$close}";
		}
	}