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我正在尝试使用带有谓词的表达式来显示每个父节点的子节点（练习看起来很傻，因为这是测试数据：最终解决方案必须从其他 xml 文件中提取数据）。

数据样本如下：

<Schools>
<School>
<name>St John's</name>
<AcademicYear year = "2017"></AcademicYear>
<Subject>English</Subject>
<Subject>Geography</Subject>
<Subject>Maths</Subject>
<AcademicYear year = "2016"></AcademicYear>
<Subject>Maths</Subject>
<Subject>Textiles</Subject>
<Subject>English</Subject>
<AcademicYear year = "2015"></AcademicYear>
<Subject>History</Subject>
<Subject>French</Subject>
<Subject>Spanish</Subject>
</School>

<School>
<name>Marsh Academy</name>
<AcademicYear year = "2017"></AcademicYear>
<Subject>Science</Subject>
<Subject>Geography</Subject>
<Subject>Computer science</Subject>
<AcademicYear year = "2016"></AcademicYear>
<Subject>English</Subject>
<Subject>History</Subject>
<Subject>Maths</Subject>
<AcademicYear year = "2015"></AcademicYear>
<Subject>French</Subject>
<Subject>Geography</Subject>
<Subject>Art</Subject>
</School>

</Schools>

查询如下：

<Schools>
{for $School in doc("test.xml")/Schools/School
return
<School>
  <Name>
  {$School/name}
  </Name>
  {for $i in doc("test.xml")/Schools/[School = $School]/AcademicYear
  return
  <AcademicYear>
    {$i/@year}
    <subject><teacher></teacher><scale></scale></subject>
  </AcademicYear>}
   </School>}
</Schools>

出现的错误显示与第 8 行相关的“预期节点，找到数组”。我尝试了 for 循环，并简单地在学年标签内放置了一个表达式，如下所示

{doc("test.xml")/Schools/[School = $School]/AcademicYear/@year}

抱歉 - 我确定这很简单。我是初学者！

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1 回答 1

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谓词之前没有子节点。

选择School元素时，将其作为从元素中选择的子节点移到谓词之外，Schools然后在谓词过滤器内，School用 引用当前元素.：

for $i in doc("test.xml")/Schools/School[. = $School]/AcademicYear

但是，如果您要遍历同一文档中的元素，为什么不直接使用已经选择的$School：

for $i in $School/AcademicYear
于 2017-12-02T00:51:50.927 回答