XQuery - XPath

食堂符合要求。 它使用XPath语来限制XML收集的搜索结果。 关于如何使用XPath的更多详情,见XPath Tutorial。

回顾我们以前曾用来拿到账簿清单的以下文字。

doc("books.xml")/books/book

XPath Examples

我们将使用这些书刊,并将其应用XQuery。

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>40.50</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>

我们在此发表了三本书,其中实现了展示价格价值超过30的图书名称的同样目标。

XQuery – Version 1

(: read the entire xml document :)
let $books := doc("books.xml")

for $x in $books/books/book
where $x/price > 30
return $x/title

Output

<title lang="en">Learn .Net in 24 hours</title>
<title lang="en">Learn XQuery in 24 hours</title>

XQuery – Version 2

(: read all books :)
let $books := doc("books.xml")/books/book

for $x in $books
where $x/price > 30
return $x/title

Output

<title lang="en">Learn .Net in 24 hours</title>
<title lang="en">Learn XQuery in 24 hours</title>

XQuery – Version 3

(: read books with price > 30 :)
let $books := doc("books.xml")/books/book[price > 30]

for $x in $books
return $x/title

Output

<title lang="en">Learn .Net in 24 hours</title>
<title lang="en">Learn XQuery in 24 hours</title>

Verify the Result

为核实结果,取代books.xqy。 (见。