Appending data to a MySQL database field that already has data in it

Append at the end of a field, separated with with a line break:

UPDATE Table SET Comment = CONCAT_WS(CHAR(10 USING UTF8), Comment, 'my comment.');

• CONCAT_WS() appends multiple strings separated by a given separator.
• CHAR(10, UTF8) is a line break.

UPDATE Table SET Field=CONCAT(Field,'your extra html');

UPDATE myTable SET html=concat(html,'<b>More HTML</b>') WHERE id='10' 

... for example. Your WHERE would be different of course.