Re: 4 the FAQ: Are Commercial DBMS Truly Relational?
Date: Sun, 10 Oct 2004 20:07:11 -0700
Message-ID: <f6tjm0ddeh47uidvbn7744avbnctab3alq_at_4ax.com>
Kenneth Downs <firstinit.lastname_at_lastnameplusfam.net> wrote:
>Gene Wirchenko wrote:
>
>> Kenneth Downs <firstinit.lastname_at_lastnameplusfam.net> wrote:
>>
>>>Gene Wirchenko wrote:
>>
>> [snip]
>>
>>>> That single, unique column is also a constrained (PK). What
>>>> happens when a key for that column is entered wrong? Why would it be
>>>> any different for another key for another unique column, say SSN?
>>
>>>The key fact about the Employee_ID column is that by definition it has no
>>>meaning, it is correct if and only if it is unique. It's only purpose is
>>>to be unique.
>>
>> An SSN is correct iff it is unique, too.
>Um, no. If you are entered with my SSN it is not correct even if unique.
And if I am entered with your employee number, it is not correct even if unique.
Sincerely,
Gene Wirchenko
Computerese Irregular Verb Conjugation:
I have preferences. You have biases. He/She has prejudices.Received on Mon Oct 11 2004 - 05:07:11 CEST