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Re: Mazes, trees, and forests

From: x <x-false_at_yahoo.com>
Date: Fri, 23 Apr 2004 11:56:58 +0300
Message-ID: <4088d9b2$1@post.usenet.com>

"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:4088c70c$0$574$e4fe514c_at_news.xs4all.nl...
> Mazes, trees, and forests.
>
> Say we have a populated database. For the ease of
> discussion let's assume it is a relational database.

> A2. Walk up from R1 along the foreign-keys of R1 to R2.
> Take the first candidate R2 to be the biggest relation
> to which an FK in R1 refers.
> Etcetera until we have a relation with no foreign keys.
> This gives us candidate tree Tree(R1,1).
> Repeat A2 until we walked all trees.
> Delete all population in the biggest tree from the
> database.

Why do you consider only the foreign-keys of R1 ? A user can connect any two relations on any two attributes of compatible types.
Do you consider only the base relations or any relation ? ;-) How can someone (other than the user) predict for what pairs of attributes the join of two relations make sense ?
This is why a relational DBMS is different from other types of DBMSs.

If you have not done this already, take a look at: http://www.scism.sbu.ac.uk/~rmkemp/codd1970.dbf http://www.scism.sbu.ac.uk/~rmkemp/codd1979.dbf

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Received on Fri Apr 23 2004 - 03:56:58 CDT

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