XQuery - How to remove empty subelement - xquery

Question

I have the following XQuery:
<a> {
for $p in doc("p.xml")//p
return
<p q="{$p/#q}> {
for $w in $p//#w
where count(doc("r.xml")//s[#w = $w]) = 0
return
<s w="{$w}"></s>
} </p>
} </a>
When I run galax-run, it will give the following result (After I formatted it):
<a>
<p q="p1">
<s w="S"/>
<s w="Sc"/>
<s w="L"/>
</p>
<p q="p2"/>
<p q="p3">
<s w="S"/>
</p>
</a>
I want to delete <p q="p2"/> in the result because there is nothing in the element. So the result I want is:
<a>
<p q="p1">
<s w="S"/>
<s w="Sc"/>
<s w="L"/>
</p>
<p q="p3">
<s w="S"/>
</p>
</a>
How do I modify the XQuery in order to get this result? Thank you in advance!

Answer 1

It isn't clear without sample input XML, but I think, you can use if-then-else construct to skip <p> elements which $content would be empty. Something like this (untested) :
<a> {
for $p in doc("p.xml")//p
let $content :=
for $w in $p//#w
where count(doc("r.xml")//s[#w = $w]) = 0
return $w
return
if($content) then
<p q="{$p/#q}"> {
for $c in $content
return
<s w="{$c}"></s>
} </p>
else ()
} </a>