find the departments with the most employees in Xquery - xquery

Question

I am trying to find the departments with the most employees (and its number of employees) in the following xml document:
<organization>
<departements>
<dept id="d1">
<name>accounting</name>
</dept>
<dept id="d2">
<name>marketing</name>
</dept>
<dept id="d3">
<name>production</name>
</dept>
</departements>
<employees>
<emp id="e1">
<name>...</name>
<activities>
<activity ref="d1"/>
</activities>
</emp>
<emp id="e2">
<name>...</name>
<activities>
<activity ref="d2"/>
<activity ref="d3"/>
</activities>
</emp>
<emp id="e3">
<name>...</name>
<activities>
<activity ref="d3"/>
</activities>
</emp>
<emp id="e4">
<name>...</name>
<activities>
<activity ref="d2"/>
</activities>
</emp>
</employees>
</organization>
Here is what i have tried:
(for $dept in doc('emp_dept.xml') //dept
let $nbr := count(doc('emp_dept.xml')//activity[#ref = $dept/#id])
order by $nbr descending
return $dept ) [1]
The above query returns the following output:
<dept id="d2">
<name>marketing</name>
</dept>
I would like to get the following output:
<dept id="d2">
<name>marketing</name>
<employees>2</employees>
</dept>
<dept id="d3">
<name>production</name>
<employees>2</employees>
</dept>

Answer 1

You could create the dept elements you want to output, determine the highest number of employees, and then output the ones that match that max count.
I'm sure there is a more efficient way, but this is what first came to mind.
let $doc := doc('emp_dept.xml')
let $newDept := for $dept in $doc//dept
return
<dept>{$dept/#*,$dept/*,
<employees>{count($doc//emp[activities/activity/#ref=$dept/#id])}</employees>
}</dept>
let $maxEmployees := max($newDept/employees)
return
$newDept[employees=$maxEmployees]