XQuery XPath

XQuery and XPath are closely related languages, and XQuery includes a subset of XPath expressions for navigating and querying XML data. XPath is a query language specifically designed for selecting elements and attributes in an XML document. XQuery, on the other hand, is a full-fledged programming language that extends XPath with additional features for processing and transforming XML data.

In XQuery, you can use XPath expressions to identify nodes within an XML document or sequence. XPath expressions are enclosed in curly braces {} and can be used in various parts of an XQuery, such as in a FLWOR expression, function arguments, or as return values.

Here are some common examples of using XPath in XQuery:

1. Selecting Elements with XPath:

let $doc := <bookstore>
            <book>
              <title>XQuery 101</title>
              <author>John Doe</author>
            </book>
            <book>
              <title>XQuery Advanced</title>
              <author>Jane Smith</author>
            </book>
          </bookstore>
return $doc/bookstore/book/title

Output:

<XQuery 101</title>
<XQuery Advanced</title>

In this example, the XPath expression /bookstore/book/title selects all <title> elements that are children of <book> elements, from the XML document stored in the variable $doc.

2. Using XPath in FLWOR Expression:

let $doc := <bookstore>
            <book>
              <title>XQuery 101</title>
              <author>John Doe</author>
            </book>
            <book>
              <title>XQuery Advanced</title>
              <author>Jane Smith</author>
            </book>
          </bookstore>
for $title in $doc//title
return $title

Output:

<XQuery 101</title>
<XQuery Advanced</title>

In this example, the FLWOR expression uses the XPath expression $doc//title to find all <title> elements in the XML document stored in the variable $doc, and then returns them.

3. Using XPath in Function Arguments:

let $doc := <bookstore>
            <book>
              <title>XQuery 101</title>
              <author>John Doe</author>
            </book>
            <book>
              <title>XQuery Advanced</title>
              <author>Jane Smith</author>
            </book>
          </bookstore>
let $author := $doc/bookstore/book/author[title = 'XQuery Advanced']
return $author

Output:

<author>Jane Smith</author>

In this example, the XPath expression $doc/bookstore/book/author[title = 'XQuery Advanced'] is used to find the <author> element whose corresponding <title> element has the value ‘XQuery Advanced’.

These examples demonstrate how XQuery uses XPath expressions to select and navigate XML data. XPath expressions allow you to specify complex criteria for locating specific nodes within an XML document, making it a powerful tool for querying and processing XML data in XQuery.