code: func (e *ShowExec) fetchShowCharset() error {
  	descs := charset.GetSupportedCharsets()
  	for _, desc := range descs {
  		e.appendRow([]interface{}{
  			desc.Name,
  			desc.Desc,
  			desc.DefaultCollation,
  			desc.Maxlen,
  		})
  	}
  	return nil
  }
docs: // fetchShowCharset gets all charset information and fill them into e.rows.
  // See http://dev.mysql.com/doc/refman/5.7/en/show-character-set.html