public function _joinUsing($type, $name, $cond, $cols = '*', $schema = null)
    {
        if (empty($this->_parts[self::FROM])) {
            // require_once 'Zend/Db/Select/Exception.php';
            throw new Zend_Db_Select_Exception("You can only perform a joinUsing after specifying a FROM table");
        }

        $join  = $this->_adapter->quoteIdentifier(key($this->_parts[self::FROM]), true);
        $from  = $this->_adapter->quoteIdentifier($this->_uniqueCorrelation($name), true);

        $cond1 = $from . '.' . $cond;
        $cond2 = $join . '.' . $cond;
        $cond  = $cond1 . ' = ' . $cond2;

        return $this->_join($type, $name, $cond, $cols, $schema);
    }