[thelist] Asking for email address twice

Bill Moseley moseley at hank.org
Thu Jan 22 12:02:51 CST 2009

On Wed, Jan 21, 2009 at 05:23:17PM -0500, r937 wrote:
>> [Please note that (a) implies (b) ...
> huh? what were (a) and (b) again?
>> don't make email address the primary key in your valid user table.]
> whyever not?  because it might change? what's wrong with updating a 
> primary key?

Because email addresses are not unique over time.  Over time the same
email address can get "recycled" and used by different people.

I did a database conversion a year or so ago where the specification
called for unique email addresses.  I quick database query showed that
there were a number of instances where the same email address belonged
to different people at different times.

Clearly, there are work-arounds to deal with this, but assuming they
are unique is a mistake.

Bill Moseley
moseley at hank.org
Sent from my iMutt

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