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XQuery Example
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Let’s learn some basic XQuery by looking at an example.
The XML Example Document
We will use the following XML document in the examples below.
“books.xml”:
Everyday Italian
Giada De Laurentiis
2005
30.00
Harry Potter
J K. Rowling
2005
29.99
XQuery Kick Start
James McGovern
Per Bothner
Kurt Cagle
James Linn
Vaidyanathan Nagarajan
2003
49.99
Learning XML
Erik T. Ray
2003
39.95
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:
doc(“books.xml”)
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:
Everyday Italian
Harry Potter
XQuery Kick Start
Learning XML
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:
Harry Potter
J K. Rowling
2005
29.99
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