THE WORLD'S LARGEST WEB DEVELOPER SITE

XML 教程

XML主页 XML简介 XML使用方法 XML Tree XML语法 XML元素 XML属性 XML命名空间 XML显示 XML HttpRequest XML解析器 XML DOM XML XPath XML XSLT XML XQuery XML XLink XML验证器 XML DTD XML模式 XML服务器 XML 示例 XML 测试 XML 证书

XML AJAX

AJAX简介 AJAX XMLHttp AJAX请求 AJAX响应 AJAX XML文件 AJAX PHP AJAX ASP AJAX数据库 AJAX应用程序 AJAX 示例

XML DOM

DOM简介归纳 DOM节点 DOM访问 DOM节点信息 DOM节点列表 DOM遍历 DOM导航 DOM获取价值 DOM变更节点 DOM删除节点 DOM替换节点 DOM创建节点 DOM添加节点 DOM克隆节点 DOM 示例

XPath 教程

XPath简介 XPath节点 XPath语法 XPath轴 XPath运算子 XPath 示例

XSLT 教程

XSLT简介 XSL语言 XSLT转换 XSLT <template> XSLT <value-of> XSLT <for-each> XSLT <sort> XSLT <if> XSLT <choose> XSLT申请 客户端上的XSLT 服务器上的XSLT XSLT编辑XML XSLT 示例

XQuery 教程

XQuery简介 XQuery示例 XQuery FLWOR XQuery HTML XQuery条款 XQuery语法 XQuery添加 XQuery选择 XQuery函数

XML DTD

DTD简介 DTD构建基块 DTD元素 DTD属性 DTD元素 vs Attr DTD实体 DTD 示例

XSD Schema

XSD简介 XSD如何 XSD <schema> XSD元素 XSD属性 XSD限制

XSD Complex

XSD元素 XSD Empty XSD元素 Only 仅限XSD文字 XSD混合 XSD指标 XSD <any> XSD <anyAttribute> XSD替代 XSD示例

XSD Data

XSD字串 XSD日期 XSD数值 XSD杂项 XSD 参考

Web Services

XML服务 XML WSDL XML SOAP XML RDF XML RSS

参考

DOM节点类型 DOM节点 DOM节点List DOM NamedNodeMap DOM文档 DOM元素 DOM属性 DOM文字 DOM CDATA DOM评论 DOM XMLHttpRequest DOM解析器 XSLT元素 XSLT / XPath函数

XQuery FLWOR Expressions


What is FLWOR?

FLWOR (pronounced "flower") is an acronym for "For, Let, Where, Order by, Return".

  • For - selects a sequence of nodes
  • Let - binds a sequence to a variable
  • Where - filters the nodes
  • Order by - sorts the nodes
  • Return - what to return (gets evaluated once for every node)

The XML Example Document

We will use the "books.xml" document in the examples below (same XML file as in the previous chapter).

View the "books.xml" file in your browser.


How to Select Nodes From "books.xml" With FLWOR

Look at the following path expression:

doc("books.xml")/bookstore/book[price>30]/title

The expression above will select all the title elements under the book elements that are under the bookstore element that have a price element with a value that is higher than 30.

The following FLWOR expression will select exactly the same as the path expression above:

for $x in doc("books.xml")/bookstore/book
where $x/price>30
return $x/title

The result will be:

<title lang="en">XQuery Kick Start</title>
<title lang="en">Learning XML</title>

With FLWOR you can sort the result:

for $x in doc("books.xml")/bookstore/book
where $x/price>30
order by $x/title
return $x/title

The for clause selects all book elements under the bookstore element into a variable called $x.

The where clause selects only book elements with a price element with a value greater than 30.

The order by clause defines the sort-order. Will be sort by the title element.

The return clause specifies what should be returned. Here it returns the title elements.

The result of the XQuery expression above will be:

<title lang="en">Learning XML</title>
<title lang="en">XQuery Kick Start</title>




W3Schools is optimized for learning and training. 示例 might be simplified to improve reading and learning. Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. While using W3Schools, you agree to have read and accepted our terms of use, cookie and privacy policy.

Copyright 1999-2021 by Refsnes Data. All Rights Reserved.
W3Schools is Powered by W3.CSS.

W3Schools.com