First XPath. Xpath refers to a position in an XML documents, I saw a good example somewhere online as I was working on this that helped me visualize it more. Suppose you want to get to some directions to a geographical location, for example you would like to go to the Bagdad Theater in Portland, Oregon (my home town), well you might write down the location something like this:
usa/or/portland/southeast/hawthorn/37ave/BagdadTheater
In XML this might look something like this:
<usa>
<or>
<portland>
<southeast>
<hawthorn>
<thirtyseventh>
</BagdadTheater>
</thirtyseventh>
</hawthorn>
</southeast>
</portland>
</or>
</usa>
The Xpath for the Bagdad Theater could be presented as we saw it above: usa/or/portland/southeast/hawthorn/37ave/BagdadTheater
That's all Xpath is, it explains where something is, then you can reference what ever is there. Simple right?
Next this leads us into Navigation.
OR:
Credit to W3schools.org for these pics!
They say a picture is worth of thousand words. This picture helped me to understand what exactly an XML tree looks like, and what the relationship is within it. It's not surprising that when it comes to navigation most books will talk about "child nodes", "siblings", "parents", and "descendants"... they do this because again XML is formatted like a tree (think family tree). So there are children, parents etc. To make navigation a little easier we have some abbreviations for the nodes:
This: // "Retrieves the context node and all its descendants"
This: @ "Retrieves the specified ATTRIBUTE (remember attributes are always in quotes) of the context node"
This: .. "Retrieves the parent of the context node" I tend to think about Linux on this one, and how to navigate folders; ".." always goes up one folder
Hopefully this clears up some navigation within XML.
I'll write more on Xquery tomorrow... cheers until then!
Credits:
wikipedia.org
w3schools.org
Querying Microsoft SQL 2012; Itzik Ben-Gan, Dejan Sarka, Ron Talmage
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