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Posted by --CELKO-- on 03/13/06 00:58
Your whoel mental model of RDBMS is wrong and it is about to kludge you
to death.
When you look for a key, start with your industry standards. I have
been in IT for a bit over 35 years, and would estimate that this covers
~80% of the properly defined systems -- VIN, ISBN, UPC, EAN, etc. which
can be verified and validated via a trusted exernal source. In the ode
days, this took time; you can Google it today.
After that, there is a natural key in the data, such as (longitude,
latitude), (store, cash register, ticket_nbr), etc. which can be
verified and validated in the reality of the data. This is ~18% of the
cases. if you have no natural key, then your schema is probably wrong.
Then, if that fails we invent a key with check digits, validation rules
and an audit trail within our enterprise. This is a great screaming
pain IF you do it right. This is why industry standards exists --
people got tired the pain (would you like to do Retail without UPC
barcodes on products?)
So, newbies prefer to do it wrong by using auto-increments or other
proprietary stuff that cannot be verified or validated BECAUSE it is
easier than real RDBMS design. It takes SIX years to become a Union
Journeyman carpenter in New York State, but newbies can be a DB
designer in less than 10 years. Hell, less than 10 months! WOW!
I know you want the quick easy answer that does not require you
ACTUALLY UNDERSTAND the business problem or your problem domain. Just
make up something in the software and hope you never write for a
company that has a SOX audit or a Data Warehouse project.
What you posted is just enough to get a lot of Kludges but not a real
answer.
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