Mark D Powell wrote:
> I agree that in relational design theory that you should not construct
> a single column where the column actually consists of multiple data
> items; however, in the real world such values do exist. These values
> are pretty much used only as a whole and their contents are not
> accessed standalone though there are exceptions. The VIN number used
> by the automotive industry is an example. The value represents
> numerous data items and its construction is actually set in law.
>
> A better example is the engine serial number used by a manufacturer I
> know of. The first two digits represent the number of cylinders and
> the two following digits represent the series. The final six digits
> are a sequential sequence from 1 to 99999. If enough units are
> produced to consume the sequence then it is reset to 1 and another
> series code is issued to allow extension of the line.
>
> Just adding another digit is not an option due to business restrictions
> including import laws of customer countries, export licenses, and the
> fact one's customer base IT systems only allow 10 digits and are
> running on computer systems that still use vacuum tubes makes changing
> the size of the column a long process.
> The real world and theory do not always agree.
>
> -- Mark D Powell --
Excellent examples of exceptions to the rule.
--
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)
Received on Mon Dec 27 2004 - 11:35:48 CST
