Re: normalization
- From: Jared Still <jkstill@xxxxxxxxx>
- To: stephenbooth.uk@xxxxxxxxx
- Date: Tue, 1 Nov 2005 17:07:05 -0800
Hi Stephen, comments inline:
On 11/1/05, stephen booth <stephenbooth.uk@xxxxxxxxx> wrote:
> Calculated fields are a breach of 3NF. But then, like most things in
> life, business applications don't always fit into nice mathematical
> models so every rule has to have an addendum something like "...unless
> there's a really good reason to do otherwise." I think it's important
> to be aware that you are breaching a rule and to spend some time
> thinking about the implications.
You make a good point in regards to 'thinking about the implications'
In real life though, it seems there are a lot of folks that have no
idea what the implications are, and will not recognize the extra
work created by those implications.
e.g. You might need a before update trigger to make sure that when any
> field that is used in a calculation is changed the fileds thaqt are
> calculated from that are recalculated. Actually you might be best to
> put the calculation in a trigger and make it a before insert or update
> if you can.
>
BEFORE UPDATE triggers have their own set of problems, and should
be used judiciously. I'm sure many of us (me) have used them in the
past more than they should have been.
http://tkyte.blogspot.com/2005/08/part-ii-seeing-restart.html
http://tkyte.blogspot.com/2005/09/part-iii-why-is-restart-important-to.html
--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
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