>>> >The notion of a "variant record" exists in many programming languages.
>>> >Typically you have a selector to indicate which variant it is. There
>>> >nothing at all wrong with using the same sort of construct in a
>>> In O-O databases. I think the concept is not defined in relational
>>> database theory. Are you aware of the rel db rule regarding domains?
>>> >The only constraint you _really_ need to meet in a database is that
>>> you let
>>> >the database product do the things it needs to do so that the queries
>>> >make are O(log N) when possible. The rest is pure fluff. Beyond that,
>>> >there is no "should".
>>> Relational theory says otherwise.
>>I'm with Peter on this one, in relational theory and data modelling,
>>a lot of very well documented "should" :-)
>You guys have been reading too many books. Books are bad.
>The key question is when something is so much different from another thing
>it is a qualitative difference rather than a quantitative difference.
>I go to the vet's office from time to time, and they keep their records in
> Is a rabbit different enough from a dog that you need different types of
> the database? Probably not. They are both pets. There may be some
>about dogs that doesn't apply to rabbits or vice-versa, but people make do.
> leave the "rabies vaccination" fields blank for a rabbit, presumably.
The notion of a "rabies vaccination" -column- is a bad thing, if this is
you've gone the wrong path. Any decent database design book will tell you
perhaps books aren't that bad?
>The "variant record" notion applies--whether it is called that or not--in
>every practical database in the world.
It still doesn't apply.
>A customer that is a person vs. a customer that is a company ... not that
>I do understand the points that are being made ... but once you get beyond
>database product being able to make queries efficiently ... it is all
Fix the product, keep the design proper.
Yet, it's not just about the database product itself, it's the idiocracies
introducing when your design goes haywire...
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