[Treffynnon]

OK, so I think this might be a language/understanding difference here - perhaps what I have written isn't clear enough - not sure. The statement to some degree, in my opinion, doesn't imply that the key isn't actually unique. It still means unique.

What I meant is that if you don't have a unique column to make, say, a primary key with then you need to make it unique by adding (an)other column(s) to it in the key definition. Each additional column being a degree of difference/separation in my mind as I was writing it.

I hope that explanation makes sense and doesn't confuse the issue further.

I'd like to get your feedback on what you think it could say to make this clearer - I want to convey:

a. it must be unique.

b. you can have multi-column keys (some users - especially those tied to an ORM - don't actually know that you can do this).