XQuery Examples
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In this section, let's learn some basic XQuery syntax by studying an example.
XML Example Document
We will use this XML document in the following example.
"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>
How to select nodes from "books.xml"?
Function
XQuery uses functions to extract data from the XML document.
doc() is used to open the "books.xml" file:
doc("books.xml")
Path expression
XQuery uses path expressions to navigate through elements in the XML document.
The following path expression is used to select all title elements in the "books.xml" file:
doc("books.xml")/bookstore/book/title
(/bookstore selects the bookstore element, /book selects all book elements under the bookstore element, and /title selects all title elements under each book element)
The above XQuery can extract the following data:
<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>
Predicate
XQuery uses predicates to limit the data extracted from the XML document.
The following predicate is used to select all book elements under the bookstore element, and the value of the price element under the selected book element must be less than 30:
doc("books.xml")/bookstore/book[price<30]
The above XQuery can extract the following data:
<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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