In case your XQuery processor does not support group by
, you will need to perform an (implicit) join. Very similar to your query, but fetch all reviewers and for each, query the reviewers using a predicate.
<query2>
<output>
{
for $reviewer in distinct-values(doc("reviews.xml")/reviews/review/reviewer)
return <reviewer>
{
/reviews/review[reviewer = $reviewer]/movie_title
}
</reviewer>
}
</output>
</query2>