protected function _buildSet()
    {
        $values = [];
        $states =  $this->_schema ? ['schema' => $this->_schema] : [];
        foreach ($this->_parts['values'] as $key => $value) {
            $states['name'] = $key;
            $values[] = $this->dialect()->name($key) . ' = ' . $this->dialect()->value($value, $states);
        }
        return $values ? ' SET ' . join(', ', $values) : '';
    }