private function _uniqueCorrelation($name)
    {
        if (is_array($name)) {
            $c = end($name);
        } else {
            // Extract just the last name of a qualified table name
            $dot = strrpos($name,'.');
            $c = ($dot === false) ? $name : substr($name, $dot+1);
        }
        for ($i = 2; array_key_exists($c, $this->_parts[self::FROM]); ++$i) {
            $c = $name . '_' . (string) $i;
        }
        return $c;
    }