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   RE: XML query engines: was RE: Is XML dead already or what?

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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 

I don't know who "invented" this trick, but I know that Joe Celko has 
written about it, perhaps he first described it.


Jarle Stabell
Digital Logikk AS

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