(:
XML Query Use Cases: http://www.w3.org/TR/xquery-use-cases/
Copyright ©2003 World Wide Web Consortium, (Massachusetts Institute of Technology, European Research Consortium for Informatics and Mathematics, Keio University). All Rights Reserved. This work is distributed under the W3C® Software License [1] in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
[1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
 Filename: rQ10.xq :)

(: Section: 1.4.4.10 Q10  For each item that has received a bid, 
  list the item number,  the highest bid, and the name of the highest bidder, ordered by item number.:)

<result>
 {
    for $highbid in doc("bids.xml")//bid_tuple,
        $user in doc("users.xml")//user_tuple
    where $user/userid = $highbid/userid 
      and $highbid/bid = max(doc("bids.xml")//bid_tuple[itemno=$highbid/itemno]/bid)
    order by $highbid/itemno
    return
        <high_bid>
            { $highbid/itemno }
            { $highbid/bid }
            <bidder>{ $user/name/text() }</bidder>
        </high_bid>
  }
</result>