在重复更新时插入表格,但保留某些列旧值

I have a myIsam table people as follow:

[id][name][cat] with values: 12,"John Doe", "worker"

id is unique and name is fulltext.

I put some values inside by a remote file call. Then I change manually cat value to another different value:

[id][name][cat] with values: 12,"John Doe", "player"

When I update values from a remote file again to insert into table, I don't want the column 'cat' get old remote values from file in case row have same id. I just want to keep the manually entered value. But still retrieving the old value!

I am trying with this code and it's doesn't work.

INSERT INTO people (id,name,cat) VALUES (12,'John Doe','worker') ON DUPLICATE KEY UPDATE name = '$name',cat = VALUES(cat);