public function values($data)
    {
        if ($this->_type !== 'insert') {
            throw new Exception(
                'You cannot add values before defining columns to use.'
            );
        }
        if (empty($this->_parts['insert'])) {
            throw new Exception(
                'You cannot add values before defining columns to use.'
            );
        }

        $this->_dirty();
        if ($data instanceof ValuesExpression) {
            $this->_parts['values'] = $data;

            return $this;
        }

        $this->_parts['values']->add($data);

        return $this;
    }