Re: Is PRIMARY KEY the same as UNIQUE NOT NULL?

On 8 February 2016 at 08:04, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Geoff Winkless <pgsqladmin@geoff.dj> writes:
>> On 31 January 2016 at 19:53, David G. Johnston
>> <david.g.johnston@gmail.com> wrote:
>>> A PRIMARY KEY enforces a UNIQUE, NOT NULL constraint and additionally allows
>> [snip]
>
>> I would just remove the whole paragraph. A primary key does what it
>> does, a unique constraint does what it does. I'm not really sure why
>> you need to link them.
>
> I think it is useful to compare them; the only problem is claiming that
> they're equivalent.
>
> I've applied some doc updates based on this discussion.
>
> http://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=c477e84fe2471cb675234fce75cd6bb4bc2cf481
>
>                         regards, tom lane

Thanks Tom,

I think with the documentation expressed this way I don't think I
would have made the error I did originally; from my point of view it
is a welcome improvement.

Cheers,

Ben