code: public function addCommentOnColumn($table, $column, $comment)
      {
          // Strip existing comment which may include escaped quotes
          $definition = trim(preg_replace("/COMMENT '(?:''|[^'])*'/i", '',
              $this->getColumnDefinition($table, $column)));
  
          return 'ALTER TABLE ' . $this->db->quoteTableName($table)
              . ' CHANGE ' . $this->db->quoteColumnName($column)
              . ' ' . $this->db->quoteColumnName($column)
              . (empty($definition) ? '' : ' ' . $definition)
              . ' COMMENT ' . $this->db->quoteValue($comment);
      }
docs: {@inheritdoc}
  @since 2.0.8