public function field($field)
    {
        if (!isset($field['name'])) {
            throw new SqlException("Missing column name.");
        }
        if (!isset($field['use'])) {
            if (isset($field['type'])) {
                $field += $this->type($field['type']);
            } else {
                $field += $this->type('string');
            }
        }
        return $field + [
            'name'      => null,
            'type'      => null,
            'length'    => null,
            'precision' => null,
            'serial'    => false,
            'default'   => null,
            'null'      => null
        ];
    }