Add character to end of field in SQL Database if condition = true? -

i want add star * end of 'displayname' field of record category of 2. not sure how think on right track?

update `table_name` set `displayname` = replace(displayname, 'old_text', 'new_text') category = '2'; 

my problem need add space , character @ end, not find , replace.

the generic sql be:

update `table_name`     set `displayname` = concat(displayname, '*') category = '2'; 

concat() can spelled in different ways depending on database -- such + or ||.