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

Gene Wirchenko wrote:

> Kenneth Downs <firstinit.lastname_at_lastnameplusfam.net> wrote:
>

>>Gene Wirchenko wrote:

>>>      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.

-- 
Kenneth Downs
Use first initial plus last name at last name plus literal "fam.net" to
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