Re: 4 the FAQ: Are Commercial DBMS Truly Relational?

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:

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     He/She has prejudices.