計算平均值的平均值

Question

我有一個很大的XML文件，其中包含有關酒店連鎖店的數據。每週，每天，每家酒店他們都會保留一些數據以供他們的報告：

<Report week="1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="report.xsd"> 
     <Days> 
      <Day id="1" naam="Monday"> 
       <Hotels> 
        <Hotel id="1" naam="Bonotel Antwerp"> 
         <Stays> 
          <Stay id="1"> 
           <Room id="1" number="1"/> 
           <Roomtype id="1" naam="oneperson" price="20.00"/> 
           <Period id="1" naam="lowseason" price="20.00"/> 
           <Formula id="1" naam="roomandbreakfast" price="20.00"/> 
           <Facilities> 
            <Facility id="1" naam="swimming" price="5.00"/> 
            <Facility id="2" naam="golf" price="20.00"/> 
           </Facilities> 
           <Guest id="1" naam="John Williams"/> 
          </Stay> 
          <Stay id="2"> 
           <Room id="2" number="2"/> 
           <Roomtype id="1" naam="oneperson" price="20.00"/> 
           <Period id="1" naam="lowseason" price="20.00"/> 
           <Formula id="1" naam="roomandbreakfast" price="20.00"/> 
           <Facilities> 
            <Facility id="2" naam="golf" price="20.00"/> 
            <Facility id="3" naam="minibar" price="10.00"/> 
           </Facilities> 
           <Guest id="2" naam="Ray Kurzweil"/> 
          </Stay> 
          <Stay id="3"> 
           <Room id="3" number="3"/> 
           <Roomtype id="2" naam="twoperson" price="40.00"/> 
           <Period id="1" naam="lowseason" price="20.00"/> 
           <Formula id="2" naam="halfpension" price="30.00"/> 
           <Facilities> 
            <Facility id="4" naam="tennis" price="20.00"/> 
            <Facility id="4" naam="tennis" price="20.00"/> 
           </Facilities> 
           <Guest id="3" naam="Stephen Hawking"/> 
          </Stay> 
         </Stays> 
        </Hotel> 
(: ... Other Hotels ... :) 
       </Hotels> 
      </Day> 
(: ... Other Days ... :) 
     </Days> 
    </Report> 

使用XQuery，我必須計算平均客人花費的費用。這是Roomtype價格，Periode價格，公式價格和設施總和的總和。我想出了這個XQuery的：

xquery version "1.0"; 
<ReportResult week="1"> 
{ 
    for $x in (1 to 7) 
    return 
     for $stays in doc("report.xml")//Report/Days/Day[@id=$x]/Hotels/Hotel[@id=1]/Stays 
     let $average := avg(
      for $v in $stays/Stay 
       return sum($v/Roomtype/@price) + sum($v/Facilities/Facility/@prijs) + sum($v/Formula/@price) + sum($v/Period/@price) 
     )   
     return 
     <AverageSpending hotel="Bonotel Antwerpen" day="{data($x)}"> 
      {data(round-half-to-even($average, 2))}  
     </AverageSpending> 
    } 
</Reportresult> 

這將產生的結果我想到：

<Reportresult week="1"> 
    <Averagespending hotel="Bonotel Antwerpen" day="1">101.67</AverageSpending> 
    <Averagespending hotel="Bonotel Antwerpen" day="2">321.67</AverageSpending> 
    (: ... etc... :) 
    <Averagespending hotel="Bonotel Antwerpen" day="2">255</AverageSpending> 
</Reportresult> 

不過，我還想來計算總的平均水平。所以所有的平均值除以7天的總和來輸出類似的東西

<TotalAverage>198,67</TotalAverage> 

但是我在計算這個總平均時遇到了麻煩。在Java中，我會使用一個總變量並將其與每個循環的計算平均值相加，但顯然這在這裏不起作用。我如何能夠用XQuery做到這一點？謝謝。

Answer 1

例如，你可以分配給一個變量您請求的第一部分，並計算出它的總平均和Concat的兩個結果：

xquery version "1.0"; 
<ReportResult week="1"> 
{ let $averages := 
for $x in (1 to 7) 
return 
    for $stays in doc("report.xml")//Report/Days/Day[@id=$x]/Hotels/Hotel[@id=1]/Stays 
    let $average := avg(
     for $v in $stays/Stay 
      return sum($v/Roomtype/@price) + sum($v/Facilities/Facility/@prijs) + sum($v/Formula/@price) + sum($v/Period/@price) 
    )   
    return 
    <AverageSpending hotel="Bonotel Antwerpen" day="{data($x)}"> 
     {data(round-half-to-even($average, 2))}  
    </AverageSpending> 
return ($averages,<TotalAverage>{avg($averages)}</TotalAverage>) 
</Reportresult>