- XQuery Tutorial
- XQuery - Home
- XQuery - Overview
- XQuery - Environment Setup
- XQuery - First Application
- XQuery - FLWOR
- XQuery - HTML Format
- XQuery - XPath
- XQuery - Sequences
- XQuery - Sequence Functions
- XQuery - String functions
- XQuery - Date Functions
- XQuery - Regular Expressions
- XQuery - If Then Else
- XQuery - Custom Functions
- XQuery Useful Resources
- XQuery - Quick Guide
- XQuery - Useful Resources
- XQuery - Discussion
XQuery - FLWOR
FLWOR is an acronym that stands for "For, Let, Where, Order by, Return". The following list shows what they account for in a FLWOR expression −
F - For - Selects a collection of all nodes.
L - Let - Puts the result in an XQuery variable.
W - Where - Selects the nodes specified by the condition.
O - Order by - Orders the nodes specified as per criteria.
R - Return - Returns the final result.
Example
Following is a sample XML document that contains information on a collection of books. We will use a FLWOR expression to retrieve the titles of those books with a price greater than 30.
books.xml
<?xml version="1.0" encoding="UTF-8"?> <books> <book category="JAVA"> <title lang="en">Learn Java in 24 Hours</title> <author>Robert</author> <year>2005</year> <price>30.00</price> </book> <book category="DOTNET"> <title lang="en">Learn .Net in 24 hours</title> <author>Peter</author> <year>2011</year> <price>70.50</price> </book> <book category="XML"> <title lang="en">Learn XQuery in 24 hours</title> <author>Robert</author> <author>Peter</author> <year>2013</year> <price>50.00</price> </book> <book category="XML"> <title lang="en">Learn XPath in 24 hours</title> <author>Jay Ban</author> <year>2010</year> <price>16.50</price> </book> </books>
The following Xquery document contains the query expression to be executed on the above XML document.
books.xqy
let $books := (doc("books.xml")/books/book) return <results> { for $x in $books where $x/price>30 order by $x/price return $x/title } </results>
Result
<title lang="en">Learn XQuery in 24 hours</title> <title lang="en">Learn .Net in 24 hours</title>
Verify Result
To verify the result, replace the contents of books.xqy (given in theEnvironment Setup chapter) with the above XQuery expression and execute the XQueryTester java program.
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