将数据附加到已经包含数据的MySQL数据库字段

I need to "add" data to a field that already contains data without erasing whats currently there. For example if the field contains HTML, I need to add additional HTML to the field. Is there a SQL call that will do this or do I need to call the data in that field, concatenate the new data to the existing data, and reload it into the database?I need to "add" data to a field that already co