Re: Auto-incrementing key or GUID for new DB ?

On Mon, Jan 25, 2016 at 6:12 PM, Vernon Hamberg
<vhamberg@xxxxxxxxxxxxxxx> wrote:

So far as I know, GUIDs are unique ON a system, not across them. I've seen
where a GUID generated on one system collides with one generated on another
system to which the original table was transferred.

Actually, GUIDs are not even guaranteed to be unique on a single
system. There are several ways of generating GUIDs, and some of them
are "more guaranteed" to be unique than other ways. There are
definitely GUID algorithms such that, *IF* everyone agreed to use the
same algorithm, then for all practical purposes, GUIDs would be unique
across systems, even without a central "GUID server".

But of course, not everyone uses such an algorithm. And most folks
don't really choose their own GUID algorithm, they just use whatever
their database, programming language, or operating system has
provided, and as you can imagine, implementations vary. And one
needn't assume some implementations are "less competent" than others;
like almost anything else, there are simply different trade-offs to be
made.

John Y.