Find same node value from main root in xquery

Question

p.xml

<documents>
  <dblp>
    <inproceedings>
      <author>John Cieslewicz</author>
      <author>Kenneth A. Ross</author>
      <author>Kenneth A. Ross</author>
    </inproceedings>
   </dblp>
   <dblp>
    <inproceedings>
      <author>Yi-Reun Kim</author>
      <author>Kyu-Young Whang</author>
      <author>John Cieslewicz</author>
    </inproceedings>
   </dblp>
 <documents>

my code is

for $c in doc("C:\Users\User\Desktop\p.xml")//documents/dblp/inproceedings
where fn:count($c/author) != fn:count(fn:distinct-values($c/author))
return $c/author

I need John Cieslewicz and Kenneth A. Ross in result but its shows only Kenneth A. Ross

Answer 1

If you want to list authors who appear multiple times, you need to count them globally in the list of all authors, not locally in the list of authors of a proceeding:

let $docs := doc("C:\Users\User\Desktop\p.xml")/documents, 
    $authors := $docs//author,
    $distinct-authors := distinct-values($authors)
for $author in $distinct-authors
where count($authors[. eq $author]) > 1 
return $author