Query with reused variables

• In the document "prices.xml", find the minimum price for each book, in the form of a minprice element with the book title as its title attribute.

<results>
 {
   let $doc := doc("prices.xml")
   for $t in distinct-values($doc/prices/book/title)
     let $p := $doc/prices/book[title = $t]/price
     return
       <minprice title="{$t}">
         { min($p) }
       </minprice>
 }
</results>

Adapted from XML Query Use Cases