Re: identity columns

71062.1056_at_compuserve.com (--CELKO--) wrote in message news:<c0d87ec0.0201121445.4c0ce7b7_at_posting.google.com>...

> But a company assigned email address can be a unique string that is
> checked to see that it is issued only once. AOL, Yahoo, et al seem to
> be able to do this with lots of people by adding a number after a name
> the customer can remember. They have a high turn over rate as well.

This is a time-sensitive key: it is only a unique identifier between two points in time. In AOL's case, your email address only uniquely identifies (part of) an account between the time you choose it and six months after you stop using it (AOL will put the email address back into the "open" after six months, if I remember correctly). Usually, AOL will ask you for your "primary screen name" (accountholder email address) when doing business with them, and this is enough to identify you in the majority of cases because usually they only care about the one customer using that screen name at the current point in time.

If all of your queries only need information about the here and now, then an email address is probably suitable, but I don't see the benefit of email address versus a machine-generated employee id.

• Brian