MySQL insert on duplicate update for non-PRIMARY key

Question

I am little confused with insert on duplicate update query. I have MySQL table with structure like this:

• record_id (PRIMARY, UNIQUE)
• person_id (UNIQU

Answer 1

How about my approach?

Let's say you have one table with a autoincrement id and three text-columns. You want to insert/update the value of column3 with the values in column1 and column2 being a (non unique) key.

I use this query (without explicitly locking the table):

insert into myTable (id, col1, col2, col3)
select tmp.id, 'col1data', 'col2data', 'col3data' from
(select id from myTable where col1 = 'col1data' and col2 = 'col2data' union select null as id limit 1) tmp
on duplicate key update col3 = values(col3)

Anything wrong with that? For me it works the way I want.