Subject:
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Re: A heirarchical database question
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 15 Nov 2000 06:22:52 GMT
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Viewed:
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86 times
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Jim Hughes wrote:
> Say you had some data that was heirarchical, e.g. a list of Lego Themes:
> What would be the best way to describe it in a DB table? Would this work OK:
> -----------------------------------
> Big table of Themes
>
> theme_parent (varchar)
> theme_name (varchar)
> theme_child(varchar)
What you've basically got there is a linked list. Although this
works well when running through memory, I've found that it's
costly if dealing with SQL queries. Imagine something that's
nested ten levels deep -- you'll have to make 10 individual
SQL queries to find out what the complete path name is. That's
not a big deal for personal use, but in a Web or shared application
it could be a hassle.
What I've done (and I'm sure there are MANY better ways to do it)
is to add another field that actually lists the path, i.e.
theme_path (varchar)
i.e. System/Aquazone/Aquasharks
If you're afraid that the data integrity is going to wane over time,
you could have a script run through the "linked list" nightly and
generate a new theme_path field.
Chris
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Message is in Reply To:
 | | A heirarchical database question
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| Hi: Here is a question for the DB experts: Say you had some data that was heirarchical, e.g. a list of Lego Themes: -- System ----- Aquazone ---...--- Aquasharks What would be the best way to describe it in a DB table? Would this work OK: ---...--- (...) (24 years ago, 15-Nov-00, to lugnet.off-topic.geek)
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