(Q15) Make an alphabetic list of publishers. Within each publisher, make a list of books, each containing a title and a price, in descending order by price.

<publisher_list>
   FOR $p IN distinct(document("bib.xml")//publisher)
   RETURN
      <publisher>
         <name> $p/text() </name> ,
         FOR $b IN document("bib.xml")//book[publisher = $p]
         RETURN
            <book>
               $b/title ,
               $b/price
            </book> SORTBY(price DESCENDING)
      </publisher> SORTBY(name)
</publisher_list>

• This query introduces the SORTBY clause, which is applied after and intermediate result has been constructed; it thus behaves differently than xsl:sort