xpath - 高级 XPath 查询

Question

我有一个如下所示的 XML 文件:

<?xml version="1.0" encoding="utf-8" ?>
<PrivateSchool>

     <Teacher id="teacher1">
         <Name>
           teacher1Name
         </Name>
    </Teacher>

    <Teacher id="teacher2">
        <Name>
            teacher2Name
        </Name>
    </Teacher>

  <Student id="student1">
    <Name>
      student1Name
    </Name>
  </Student>

  <Student id="student2">
    <Name>
      student2Name
    </Name>
  </Student>

    <Lesson student="student1" teacher="teacher1"  />
    <Lesson student="student2" teacher="teacher2"  />
    <Lesson student="student3" teacher="teacher3"  />
    <Lesson student="student1" teacher="teacher2"  />
    <Lesson student="student3" teacher="teacher3"  />
    <Lesson student="student1" teacher="teacher1"  />
    <Lesson student="student2" teacher="teacher4"  />
    <Lesson student="student1" teacher="teacher1"  />

</PrivateSchool>

还有一个与此 XML 相关的 DTD，但我认为它与我的问题没有太大关系。让我们假设所有需要的教师和学生都有明确的定义。

返回教师姓名的 XPath 查询是什么，其中至少有一名学生与他们一起上了 10 节课？

我正在查看许多 XPath 站点/示例。对于这种问题，似乎没有什么足够先进的了。

Answer 1

在单个 XPath 中进行复杂的连接可能是可能的，但是您的头撞在了砖墙上。 XQuery 或 XSLT 更适合这种事情。这是在 XQuery 中:

declare variable $doc as doc('data.xml');

declare function local:numLessons($teacher, $student) {
  return count($doc//Lesson[@teacher = $teacher and @student = $student])
};

$doc//Teacher[some $s in //Lesson/@student satisfies local:numLessons(@id, $s) gt 10]/Name

这样做之后，如果您真的下定决心，可以将其简化为 XPath 2.0:

doc('data.xml')//Teacher[
   for $t in . return 
     some $s in //Lesson/@student satisfies 
       count(//Lesson[@teacher = $t and @student = $s]) gt 10] /Name

未测试。