Gail Shaw wrote:

> Yup. You know the theory.

Well, and the practice of backing up and restoring a production 
database. But really, that's not especially hard if everything has been 
configured right... [You just need to DAMN WELL make sure you can do it 
in your sleep though.]

> In practice however things are sometimes done
> differently. Not because theory is wrong, but because sometimes shortcuts
> are necessary.

This part I understand.

> In theory, you want to prevent any form of data anomaly from multiple
> accesses. In reality, that often reduces concurrency to unacceptable levels,
> so some possible anomolies are accepted to get higher throughput.

Hence the various transaction isolation levels we spent so much time 
numbing our brains with, I take it...

Never came across anybody arguing that we should go for the very lowest 
option though. (Usually more like "the top option is best, but the one 
just below it is very much faster with only a couple of drawbacks"...)

> In theory, all tables should be at least 3rd normal form of Boyce-Codd
> normal form. In reality, you will get tables that are intentionally in 1st
> or 2nd normal form.

"Flexing the model?"

As in, use the theory, work out the theoretically ideal configuration, 
and then denormalise from there, making a note of what extra hoops you 
have to jump through with each denormalisation step and making sure the 
payoff is worth it. Is the way they taught us anyway... we never 
actually got as far as doing that in practice.

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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