File: Data.xml
<order>
<car model="A">
<id>1</id>
<name language="en">name 1</name>
</car>
<car model="B">
<id>2</id>
<name language="en">name 2</name>
</car>
<car model="B">
<id>3</id>
<name language="en">name 3</name>
</car>
</order>
File: Query.xquery
let $prods := doc("Data.xml")//car
for $d in distinct-values($prods/@model),
$n in distinct-values($prods[@model = $d]/id)
return <result model="{$d}" id="{$n}"/>
Output:
<?xml version="1.0" encoding="UTF-8"?>
<result id="1" model="A"/>
<result id="2" model="B"/>
<result id="3" model="B"/>