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XQuery

XQuery

Priscilla Walmsley (pwalmsley@datypic.com)

ISBN: 0596006349

1st edition, 2007, O'Reilly Media, Inc.

Chapter 24: XQuery for SQL users

Example 24-1. Product catalog document (catalog2.xml)
<catalog>
  <product dept="WMN">
    <number>557</number>
    <name>Fleece Pullover</name>
  </product>
  <product dept="ACC">
    <number>563</number>
    <name>Floppy Sun Hat</name>
  </product>
  <product dept="ACC">
    <number>443</number>
    <name>Deluxe Travel Bag</name>
  </product>
  <product dept="MEN">
    <number>784</number>
    <name>Cotton Dress Shirt</name>
    <desc>Our favorite shirt!</desc>
  </product>
</catalog>
Example 24-2. Distinctness on a combination of values
for $d in distinct-values(doc("catalog2.xml")//product/@dept),
    $n in distinct-values(doc("catalog2.xml")//product[@dept = $d]/number)
return <result dept="{$d}" number="{$n}"/>
Example 24-3. Two-way join in XQuery
for $item in doc("order.xml")//item,
    $product in doc("catalog2.xml")//product
where $item/@num = $product/number
return <item num="{$item/@num}"
             name="{$product/name}"
             quan="{$item/@quantity}"/>
Example 24-4. Grouping in XQuery
for $d in distinct-values(doc("catalog2.xml")//product/@dept)
return
  <result dept="{$d}"
          count="{count(doc("catalog2.xml")//product[@dept = $d])}"/>
Example 24-5. SQL/XML query
<SELECT c.number,
       XMLELEMENT ( NAME "product",
                    XMLATTRIBUTES (
                      c.dept AS "dept",
                      c.name AS "prodname",
                   ) AS "product_as_xml">FROM catalog c;
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