>>I didn't say he shouldn't use it as a candidate index. If he needs to keep that combination of fields unique, and as long as they aren't used for a primary key, or updating, or a relation, what would be the problem? Is it a question of reverting correctly in a heavy multi-user environment?
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>Sorry, I read you response too fast. As long as he don't use a composite key as a primary or candidate key, in my opinion, there's no real disadvantage of using it.

I think you are still reading it too fast. What is wrong with using it as a candidate key? What other kind of key is there?