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- From: Jarle Stabell <jarle.stabell@dokpro.uio.no>
- To: "'xml-dev@ic.ac.uk'" <xml-dev@ic.ac.uk>
- Date: Sun, 31 Jan 1999 20:49:57 +0100
Borden, Jonathan wrote:
> The problem with a straight relational approach is that we need to model
> containment and heirarchies... in SQL terms this means joins, perhaps
> multilevel joins when documents are deep.
There exists a neat trick which enables simple SQL-Select queries answering
for two given nodes, whether one is a subnode of the other, and also how
many levels deep, in constant time, assuming you do some simple
preprocessing on the structure. (Assigning two integers to each node in the
tree).
I don't know who "invented" this trick, but I know that Joe Celko has
written about it, perhaps he first described it.
Cheers,
Jarle Stabell
Digital Logikk AS
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