David Fetter <david@fetter.org> writes:
> On Fri, Jul 18, 2008 at 03:04:08PM +0200, Markus Schiltknecht wrote:
>> But what do we have primary keys for, in the first place?
> We have them because people are used to thinking in terms of a
> "PRIMARY KEY," not because that concept is actually distinguishable
> from a non-partial UNIQUE NOT NULL constraint.
No, we have them because the SQL standard actually assigns a distinct
meaning to a primary key. (It's the default foreign key reference
column(s) for the table --- and in that context it's clear that
There Can Be Only One.)
regards, tom lane
