Subject:
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Re: BI Portal site re-launches!
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 10 Jul 2002 12:15:47 GMT
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Viewed:
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896 times
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In lugnet.build, Jude Beaudin writes:
> In lugnet.build, Larry Pieniazek writes:
> > In lugnet.build, Jake McKee writes:
> > > In lugnet.build, Ross Crawford writes:
> > >
> > > > As Oliver says, de-normalising the database may be an effective way of
> > > > reducing the server load. Store the tree total against each category, and
> > > > update it when a link is submitted.
> > >
> > > Can you explain this a little more? I intrigued by the concept, and
> > > completely confused. My (limited) knowledge of databases tells me that
> > > normalizing the DB is a way to add efficiency. What I am missing in your
> > > suggestion?
> >
> > Normalising makes things more space efficient (by reducing storage of
> > redundant information), denormalising makes things more efficient at runtime
> > (by reducing joins).
> >
> > Storing the tree total against each category is an example of keeping
> > redundant data instead of calculating it on the fly (I forget if this is a
> > kind of denormalization or not and if it is I forget whether it's "first
> > normal form" or "second normal form" or what... I play a DBA at clients but
> > am not one, technically). Rather than doing a query to calculate the total
> > when you are asked to, you store the info and recalculate when you know the
> > value would have changed (when someone adds or removes something).
> >
> > Other kinds of time/space tradeoffs include things like moving code table
> > values into the main rows.
> >
> > Try this URL:
> >
> > http://www.palslib.com/Fundamentals/Database_Design.html
> >
> > particularly this article
> >
> > http://www.dbpd.com/vault/9804date.htm
> >
> > Note that fully normalized databases are the most compact and have no
> > redundant information (and thus have the highest data integrity) but also
> > are the slowest.
>
> The downside to denormalizing is you have to remember to update your data in
> several places whenever you update it.
>
> Depending on how complex you want to make your code it can be worth it to
> denormalize in some places to allow quicker searches. Databases are as much
> art as science. You are better to design the data model in third normal form
> and figure out where you will denormalize it than design it denormalized to
> begin with. (Follow the rules before you use the exceptions) This way you
> can have the best of both worlds, efficient size and speed.
It also depends on the database usage - if updates are frequent,
de-normalised databases start losing their efficiency, but with a database
such as this, that shouldn't be a big issue.
You can make the update code simpler by using stored procedures and / or
triggers. You can write a trigger on "insert instruction" to add 1 to the
category count, etc., then whenever a new link is submitted the category
total is always updated correctly.
ROSCO
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Message has 1 Reply:
Message is in Reply To:
 | | Re: BI Portal site re-launches!
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| (...) The downside to denormalizing is you have to remember to update your data in several places whenever you update it. Depending on how complex you want to make your code it can be worth it to denormalize in some places to allow quicker searches. (...) (22 years ago, 9-Jul-02, to lugnet.build, lugnet.off-topic.geek)
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