XQuery get distinct values

Question

Im new to XQuery and are trying to learn how to use it with BaseX.

I have this xml containing multiple elements of program:

<program id="4565">
        <name>Musiken i P3</name>
        <url>http://sverigesradio.se/sida/default.aspx?programid=4565</url>
        <editor>Anna-Karin Larsson</editor>
        <channel>164</channel>
        <category>5</category>
</program>

So far i have understod that i can get the distinct values of for example editor like such:

let $vals := $sr/sr/programs/program/editor
let $uniqe-items := distinct-values($vals)

for $vals in $uniqe-items
    order by $vals
    return <li>{string($vals)}</li>

However when i do this I only get the editors name and I can't understand how i also check something like this:

 let $vals := $sr/sr/programs/program/editor
 let $uniqe-items := distinct-values($vals)

 for $vals in $uniqe-items
     where $vals/channel = "132"
     order by $vals
     return <li>{string($vals)}</li>

I was thinking that i could do something like $vals/../channel to get back to the channel attribute but that doesn't seem to be the case.

Answer 1

Please try the following solution. I am using BaseX 9.5

The distinct-values() gives a sequence of strings: Anna-Karin Larsson, Anna Karenina, not the XML elements.

It is possible to eliminate where clause completely by using XPath predicate in the for clause:

for $vals in distinct-values(./programs/program[channel = "132"]/editor)

XQuery

xquery version "3.1";

declare context item := document {
<programs>
    <program id="4565">
        <name>Musiken i P3</name>
        <url>http://sverigesradio.se/sida/default.aspx?programid=4565</url>
        <editor>Anna-Karin Larsson</editor>
        <channel>164</channel>
        <category>5</category>
    </program>
    <program id="4770">
        <name>Musiken i P3</name>
        <url>http://sverigesradio.se/sida/default.aspx?programid=4565</url>
        <editor>Anna Karenina</editor>
        <channel>132</channel>
        <category>55</category>
    </program>
</programs>  
};

<ul>
{
  for $vals in distinct-values(./programs/program[channel = "132"]/editor)
  (:where ./programs/program[editor = $vals]/channel = "132":)
  order by $vals
  return <li>{data($vals)}</li>
}
</ul>

Output

<ul>
  <li>Anna Karenina</li>
</ul>