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POHow can I use XPath to select distinct elements based on multiple child elements?
 

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  1. POHow can I use XPath to select distinct elements based on multiple child elements?
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    <p>I need to use XPath to select distinct elements based on multiple child elements.</p> <p>I have some XML like this:</p> <pre><code>&lt;Cars&gt; &lt;Car&gt; &lt;Make&gt;SuperCar&lt;/Make&gt; &lt;Year&gt;2009&lt;/Year&gt; &lt;/Car&gt; &lt;Car&gt; &lt;Make&gt;SuperCar&lt;/Make&gt; &lt;Year&gt;2010&lt;/Year&gt; &lt;/Car&gt; &lt;Car&gt; &lt;Make&gt;AwesomeCar&lt;/Make&gt; &lt;Year&gt;2010&lt;/Year&gt; &lt;/Car&gt; &lt;Car&gt; &lt;Make&gt;SuperCar&lt;/Make&gt; &lt;Year&gt;2009&lt;/Year&gt; &lt;/Car&gt; &lt;/Cars&gt; </code></pre> <p>And I need to use XPath (I'm limited to XPath 1.0) to select only distinct elements, where distinct is defined by both <code>Make</code> and <code>Year</code>. </p> <p>In the example above this would mean returning all of the <code>Car</code> objects except the last one (as this is a duplicate of the first <code>Car</code>).</p> <p>In a typical situation (i.e. where objects were identified by a single key field) I would use an XPath similar to this:</p> <pre><code>/*/Car[not(./Id/text()=following-sibling::Car/Id/text())] </code></pre> <p>However, I can't quite work out how to adapt this to correctly use multiple fields.</p> <p>I considered something like this:</p> <pre><code>/*/Car[not(./Make/text()=following-sibling::Car/Make/text() and ./Model/text()=following-sibling::Car/Model/text())] </code></pre> <p>But that checks if the <code>Make</code> is used anywhere and if the <code>Model</code> is used anywhere, without ensuring that they are necessarily used on the same <code>Car</code>. For example it incorrectly excludes the first <code>Car</code> from the following sample XML:</p> <pre><code>&lt;Cars&gt; &lt;Car&gt; &lt;Make&gt;SuperCar&lt;/Make&gt; &lt;Year&gt;2009&lt;/Year&gt; &lt;/Car&gt; &lt;Car&gt; &lt;Make&gt;SuperCar&lt;/Make&gt; &lt;Year&gt;2010&lt;/Year&gt; &lt;/Car&gt; &lt;Car&gt; &lt;Make&gt;AwesomeCar&lt;/Make&gt; &lt;Year&gt;2009&lt;/Year&gt; &lt;/Car&gt; &lt;/Cars&gt; </code></pre> <p>Any ideas?</p>
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    1. USMatt Mitchell
    1. USMatt Mitchell
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    1. COYou might be able to do this with `<xsl:key...>` and the `key()` function.
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      1. POHow can I use XPath to select distinct elements based on multiple child elements?
      1. USJim Garrison
 

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