XQuery - return unique values without distinct-values

Question

I've come to a complete stand-still regarding a certain XQuery-problem. In the beginning, I did not have multiple exhibits with the same title in the XML-document - when I changed that I noticed a certain problem: the result (in XQuisitor) displays all the names of the guides twice or thrice for each unique exhibit, depending the how many exhibits share the same title.

I have no idea why and would be grateful for some input.

Here's the XQuery code I tried with:

for $u in (//Exhibit/@title)
let $guide := for $g in //Guide[../@title=$u]/@gname return element Guide {$g}
return element Exhibit {attribute Title {$u}, $guide }

Example XML-document:

<?xml version="1.0" encoding="UTF-8"?>
<Exhibits>
<Exhibit title = "Renaissance"  sdate= "2011-09-05"  
edate= "2012-02-05"  sarea = "2400">
<Guide gname = "John Smith" >
<Lang sname ="English"/>
<Lang sname ="German"/>
</Guide>
<Guide gname = "Weber Schneider">
<Lang sname = "German"/>
</Guide>
<Guide gname = "Robert Lundstrom">
<Lang sname = "Swedish"/>
</Guide>
<Guide gname = "Paula Munoz">
<Lang sname = "Spanish"/>
<Lang sname = "German"/>
<Lang sname = "English"/>
</Guide>
</Exhibit>
<Exhibit title = "Renaissance"  sdate= "2011-10-06" 
edate= "2011-11-26" sarea = "2000">
<Guide gname = "John Smith">
<Lang sname ="English"/>
<Lang sname ="German"/>
</Guide>
<Guide gname = "Paula Munoz">
<Lang sname = "Spanish"/>
<Lang sname = "German"/>
<Lang sname = "English"/>
</Guide>
</Exhibit>
</Exhibits>

Thanks!

Answer 1

Use:

let $vals := /*/Exhibit/@title
  return
     for $t in  $vals[index-of($vals, .)[1]]
       return
        element Exhibit 
           { attribute Title {$t},
             let $gvals := /*/Exhibit[@title eq $t]/Guide/@gname
              return
                for $gname in $gvals[index-of($gvals, .)[1]]
                  return
                    element Guide {attribute gname {$gname}} 
           }

When applied on this XML document (the provided one, made slightly more complex):

<Exhibits>
  <Exhibit title = "Renaissance"  sdate= "2011-09-05"   edate= "2012-02-05"  sarea = "2400">
    <Guide gname = "John Smith" >
      <Lang sname ="English"/>
      <Lang sname ="German"/>
    </Guide>
    <Guide gname = "Weber Schneider">
      <Lang sname = "German"/>
    </Guide>
    <Guide gname = "Robert Lundstrom">
      <Lang sname = "Swedish"/>
    </Guide>
    <Guide gname = "Paula Munoz">
      <Lang sname = "Spanish"/>
      <Lang sname = "German"/>
      <Lang sname = "English"/>
    </Guide>
  </Exhibit>
  <Exhibit title = "Renaissance"  sdate= "2011-10-06"  edate= "2011-11-26" sarea = "2000">
    <Guide gname = "John Smith">
      <Lang sname ="English"/>
      <Lang sname ="German"/>
    </Guide>
    <Guide gname = "Paula Munoz">
      <Lang sname = "Spanish"/>
      <Lang sname = "German"/>
      <Lang sname = "English"/>
    </Guide>
  </Exhibit>
  <Exhibit title = "Middle Age"  sdate= "2011-10-06"  edate= "2011-11-26" sarea = "2000">
    <Guide gname = "John Smith">
      <Lang sname ="English"/>
      <Lang sname ="German"/>
    </Guide>
    <Guide gname = "Paula Munoz">
      <Lang sname = "Spanish"/>
      <Lang sname = "German"/>
      <Lang sname = "English"/>
    </Guide>
  </Exhibit>
  <Exhibit title = "Middle Age"  sdate= "2011-09-05"   edate= "2012-02-05"  sarea = "2400">
    <Guide gname = "John Smith" >
      <Lang sname ="English"/>
      <Lang sname ="German"/>
    </Guide>
    <Guide gname = "Weber Schneider">
      <Lang sname = "German"/>
    </Guide>
    <Guide gname = "Robert Lundstrom">
      <Lang sname = "Swedish"/>
    </Guide>
    <Guide gname = "Paula Munoz">
      <Lang sname = "Spanish"/>
      <Lang sname = "German"/>
      <Lang sname = "English"/>
    </Guide>
  </Exhibit>
</Exhibits>

the wanted, correct result is produced:

<Exhibit Title="Renaissance">
   <Guide gname="John Smith"/>
   <Guide gname="Weber Schneider"/>
   <Guide gname="Robert Lundstrom"/>
   <Guide gname="Paula Munoz"/>
</Exhibit>
<Exhibit Title="Middle Age">
   <Guide gname="John Smith"/>
   <Guide gname="Paula Munoz"/>
   <Guide gname="Weber Schneider"/>
   <Guide gname="Robert Lundstrom"/>
</Exhibit>

Explanation:

We use the fact that for a sequence of atomic values $vals:

$vals[index-of($vals, .)[1]]

produces a set of items with all distinct values contained in $vals.

Answer 2

For each unique exhibit, your query finds all guides beneath any exhibits with the same name and shows these. If you only want those from the current one, try this query:

for $e in //Exhibit
let $guide := for $g in $e/Guide/@gname return element Guide {$g}
return element Exhibit {attribute Title { $e/@title }, $guide }

With the input file you provided, your query returns:

<Exhibit Title="Renaissance">
  <Guide gname="John Smith"/>
  <Guide gname="Weber Schneider"/>
  <Guide gname="Robert Lundstrom"/>
  <Guide gname="Paula Munoz"/>
  <Guide gname="John Smith"/>
  <Guide gname="Paula Munoz"/>
</Exhibit>
<Exhibit Title="Renaissance">
  <Guide gname="John Smith"/>
  <Guide gname="Weber Schneider"/>
  <Guide gname="Robert Lundstrom"/>
  <Guide gname="Paula Munoz"/>
  <Guide gname="John Smith"/>
  <Guide gname="Paula Munoz"/>
</Exhibit>

and the corrected one yields:

<Exhibit Title="Renaissance">
  <Guide gname="John Smith"/>
  <Guide gname="Weber Schneider"/>
  <Guide gname="Robert Lundstrom"/>
  <Guide gname="Paula Munoz"/>
</Exhibit>
<Exhibit Title="Renaissance">
  <Guide gname="John Smith"/>
  <Guide gname="Paula Munoz"/>
</Exhibit>