Printed 2015/10/13 05:23PM

SQL Server XQuery For Idiots

By Grant Fritchey, 2009/11/30

I’m still struggling with learning XQuery. My latest little revelation was small, but vital.

The difference between:




Is the difference between a 10 minute query and a 4 second query. Kind of shocking really. My understanding is that XQuery assumes there are multiple possible paths that look like “/rss/channel” so it searches over and over again through the XML to see if it can find them. But by identifying it as a root, showing that only one possible path is available, it stops stumbling around in the dark and simply reads the data.

It’s a little thing, but it made an enormous difference. I’ve still got a long way to go in learning how to use XPath within XQuery.

UPDATED: I modified the title so that it’s clear I’m talking about SQL Server here.

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