MySQL UPDATE to text

Hey there people, I know you can update a variable in a table using

$query = "UPDATE ad SET del = del+1 WHERE username = 'john' ";

(so that ‘del’ is actually incremented by 1 or whatever you want)

I’d like to do this with a text variable but it won’t let me:

$query = "UPDATE ad SET comment = comment + '<br>this is a new line of text' WHERE username = 'john' "

Here 'comment is a ‘TEXT’ column (similar to BLOB)

How can I do this, do I have to retrieve the whole field and then update it ?

Oh, and does anyone know how I can place linebreak (like ‘/n’) in my mysql table, so it looks cleaner ?