xquery select different tuple combinations
<p>I need to select the different combinations of countries out of the following example:</p>

<pre><code>&lt;neighbors&gt;
    &lt;neighbor&gt;
        &lt;country&gt;Greece&lt;/country&gt;
        &lt;country&gt;Albania&lt;/country&gt;
    &lt;/neighbor&gt;

    &lt;neighbor&gt;
        &lt;country&gt;Albania&lt;/country&gt;
        &lt;country&gt;Greece&lt;/country&gt;
    &lt;/neighbor&gt;
&lt;/neighbors&gt;
</code></pre>

<p>The idea is that, for this example, the combination Greece-Albania appears just once in the end result (regardless of the their order). As you can imagine, this must be done using XQuery.</p>