使用XQuery计算平均值

Question

我需要使用XQuery计算每个课程的平均值。

这里的XML代码：

<?xml version="1.0" encoding="ISO-8859-1" ?> 
<?xml-stylesheet href="class.xsl" type="text/xsl" ?> 
<university> 
<student><sname>Charlie Parker</name> 
<course sigle="INF8430" note="69" /> 
<course sigle="INF1030" note="65" /> 
<course sigle="INF1230" note="73" /></student> 
<student><name>Miles Davis</name> 
<course sigle="INF8430" note="65" /> 
<course sigle="INF1030" note="77" /> 
<course sigle="INF1230" note="83" /></student> 
<student><name>John Coltrane</name> 
<course sigle="INF9430" note="24" /> 
<course sigle="INF1030" note="64" /> 
<course sigle="INF1230" note="56" /></student> 
<student><name>Charles Mingus</name> 
<course sigle="INF8430" note="34" /> 
<course sigle="INF1230" note="89" /></student> 
</university> 

输出文件应该是这样的：

<list> 
<course sigle="INF8430">85</course> 
<course sigle="INF1030">76.66666666666667</course> 
<course sigle="INF1230">81.5</course> 
<course sigle="INF9430">39</course> 
</list> 

非常感谢您的帮助！

Answer 1

element list { 
    let $courses := doc('mydoc.xml')/university/student/course 
    for $id in distinct-values($courses/@sigle) 
    let $values := $courses[@sigle = $id]/xs:double(@note) 
    return element course { 
    attribute sigle { $id }, 
    fn:avg($values) 
    } 
}