Re: PRIMARY KEYS

On Thursday, May 22, 2003, at 11:43 AM, wsheldah@lexmark.com wrote:

>
> Choosing an artificial key is the ideal, according to everything I've
> heard. In one of my database classes, I remember I had a classmate who 
> had
> worked with some very large datasets of U.S. citizens, and found that 
> there
> were actually duplicate social security numbers assigned to different
> people. Not many, and I don't recall whether the first person had died
> before the SSN was reused, but it really goes to show that they only to
> _guarantee_ a unique primary key is to generate it yourself. Yes, you 
> may
> want to put a unique index on your SSN field or other candidate key 
> fields
> that ought to be unique.
>
> [snip]

Wouldn't one wish to know, and deal with, a situation where a business 
rule -- each person has a unique social security number -- has been 
violated? If you're a business doing tax withholding for employees, 
isn't this a critical question?