XQuery Example
Let's try to learn some basic XQuery syntax by looking at an example.
The XML Example Document
We will use the following XML document in the examples below.
"books.xml":
<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<price>49.99</price>
</book>
<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore> |
View the "books.xml" file in your browser.
How to Select Nodes From "books.xml"?
Functions
XQuery uses functions to extract data from XML documents.
The doc() function is used to open the "books.xml" file:
Path Expressions
XQuery uses path expressions to navigate through elements in an XML document.
The following path expression is used to select all the title elements in
the "books.xml" file:
| doc("books.xml")/bookstore/book/title |
(/bookstore selects the bookstore element, /book selects all the book elements
under the bookstore element, and /title selects all the title elements under each book element)
The XQuery above will extract the following:
<title lang="en">Everyday Italian</title>
<title lang="en">Harry Potter</title>
<title lang="en">XQuery Kick Start</title>
<title lang="en">Learning XML</title> |
Predicates
XQuery uses predicates to limit the extracted data from XML documents.
The following predicate is used to select all the book elements under
the bookstore element that have a price element with a value that is less than
30:
| doc("books.xml")/bookstore/book[price<30] |
The XQuery above will extract the following:
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book> |
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