如何使XQuery提取XML文档中的所有匹配节点

Question

I'm very new to XQuery and know that this is probably an easy answer but I just can't wrap my head around this one.

I have an XML file like so:

<EventLog>
  <SongSet>
    <Song SongID="S002">
      <Title>Band on the Run</Title>
      <Composer>Paul McCartney</Composer>
      <Duration>1.15</Duration>
    </Song>
    <Song SongID="S003">
      <Title>Come on Over</Title>
      <Composer>Shania Twain</Composer>
      <Duration>3.15</Duration>
    </Song>
   </SongSet>
  <ContestantSet>
   <Contestant Name="Randy Stuss" Hometown="Ottawa">
      <Repertoire>
        <SongRef>S002</SongRef>
        <SongRef>S003</SongRef>
      </Repertoire>
     </Contestant>
     <Contestant Name="Fletcher Gee" Hometown="Toronto">
      <Repertoire>
        <SongRef>S002</SongRef>
        <SongRef>S003</SongRef>
      </Repertoire>
    </Contestant>
  </ContestantSet>
</EventLog>

I need the output to look like this:

<songs> 
  <song> 
    <name> SONG NAME1 </name>
    <composer> COMPOSER NAME </composer>
    <singers>
      <singer>Singer1 Name  </singer>  
      <singer>Singer2 Name  </singer>  
    </singers>
  </song>
<songs>

I can do all of it except for getting the names of the singers together. My output looks like this:

<Songs
  <Song>
    <Title>Band on the Run</Title>
    <Composer>Paul McCartney</Composer>
    <Singers>
      <Singer>Fletcher Gee</Singer>
    </Singers>
  </Song>
  <Song>
    <Title>Band on the Run</Title>
    <Composer>Paul McCartney</Composer>
  <Singers>
    <Singer>Randy Stuss</Singer>
  </Singers>
  </Song>
</Songs>

And Here is my XQuery code:

for $x in //SongSet/Song 
for $y in //ContestantSet/Contestant 
where $x/@SongID = $y/Repertoire/SongRef 
return <Song><Title>{data($x/Title)}</Title>
       <Composer>{data($x/Composer)}</Composer>
       <Singers><Singer>{data($y/@Name)}</Singer></Singers></Song>

Where am I going wrong?

Thank you for your help!!!!

Answer 1

One possible way; loop over <Song> elements and then for the return <Singers> part loop over the matching <Contestant> elements :

for $x in //SongSet/Song 
return <Song><Title>{data($x/Title)}</Title>
       <Composer>{data($x/Composer)}</Composer>
       <Singers>{for $y in //ContestantSet/Contestant[Repertoire/SongRef = $x/@SongID]
                 return <Singer>{data($y/@Name)}</Singer>}</Singers></Song>

Xpathtester Demo

when tested aginst the XML in question, the output is as expected :

<?xml version="1.0" encoding="UTF-8"?>
<Song>
   <Title>Band on the Run</Title>
   <Composer>Paul McCartney</Composer>
   <Singers>
      <Singer>Randy Stuss</Singer>
      <Singer>Fletcher Gee</Singer>
   </Singers>
</Song>
<Song>
   <Title>Come on Over</Title>
   <Composer>Shania Twain</Composer>
   <Singers>
      <Singer>Randy Stuss</Singer>
      <Singer>Fletcher Gee</Singer>
   </Singers>
</Song>