XQuery/XPath：如何获取与另一个元素值相比具有较低元素值的元素

Question

我将举一个例子来更好地解释我自己：

<company>
    <products>
        <product ean="111">
            <listingPrice>100</listingPrice>
        </product>
        <product ean="222">
            <listingPrice>500</listPrice>
        </product>
        <product ean="333">
            <listingPrice>1000</listingPrice>
        </product>
    </products>
    <shops>
       <shop id="1">
         <product>
           <ean>111</ean>
           <sellingPrice>90</sellingPrice>      
        </product>
       </shop>

       <shop id="2">
         <product>
           <ean>888</ean>
           <sellingPrice>10</sellingPrice>      
        </product>
         <product>
           <ean>222</ean>
           <sellingPrice>300</sellingPrice>     
        </product>
       </shop>

        <shop id="3">
         <product>
           <ean>222</ean>
           <sellingPrice>600</sellingPrice>     
        </product>
       </shop>


       <shop id="4">

         <product>
           <ean>111</ean>
           <sellingPrice>20</sellingPrice>      
        </product>

         <product>
           <ean>333</ean>
           <sellingPrice>140</sellingPrice>     
        </product>


       </shop>
   </shops>
</company>

我想展示所有售价至少比上市价格低 20%的产品，并且必须是相同的产品才能比较价格。 最后显示商店 ID 及其产品 ean、售价和标价。

示例解决方案将是：

<shop id="2">
     <product ean="222" sellingPrice="300" listingPrice="500"/>
  </shop>

  <shop id="4">
     <product ean="111" sellingPrice="20" listingPrice="100"/>
     <product ean="333" sellingPrice="140" listingPrice="1000"/>
  </shop>

到目前为止我得到了什么：

let $a := fn:doc('shop.xml'),
      $b := $a//products/* ,
      $c:= $a//shops/*
return 

for $x in $c
  let $z:=
 if ($x/product/ean = $b/@ean and $x/product/sellingPrice < $b/(listingPrice *0.8 ) )
 then 
 <shop id="{$x/@*}">
<product ean="{$x/product/ean}" sellingPrice="{$x/product/sellingPrice}" listingPrice="{$b/listingPrice}"/>
</shop>

return $z

我错过了什么？

Answer 1

我认为它有助于分解出要在函数中重用的引用和比较，我也喜欢使用! map 运算符使表达式更紧凑：

declare variable $factor as xs:decimal external := 0.8;

declare function local:listing-price($product as element(product)) as xs:decimal?
{
    root($product)/company/products/product[@ean = $product/ean]/listingPrice
};

declare function local:check-price($product as element(product), $factor as xs:decimal) as xs:boolean
{
    $product/sellingPrice < local:listing-price($product) * $factor
};


/company/shops/shop[product[local:check-price(., $factor)]] 
!
<shop id="{@id}">{
    product[local:check-price(., $factor)] 
    ! 
    <product ean="{ean}" sellingPrice="{sellingPrice}" listingPrice="{local:listing-price(.)}" />
}</shop>

https://xqueryfiddle.liberty-development.net/nc4P6y7

要从文件加载，您可以在路径前加上doc()调用：

declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization";

declare option output:method 'xml';
declare option output:indent 'yes';

declare variable $factor as xs:decimal external := 0.8;

declare function local:listing-price($product as element(product)) as xs:decimal?
{
    root($product)/company/products/product[@ean = $product/ean]/listingPrice
};

declare function local:check-price($product as element(product), $factor as xs:decimal) as xs:boolean
{
    $product/sellingPrice < local:listing-price($product) * $factor
};


doc('https://github.com/martin-honnen/martin-honnen.github.io/raw/master/xslt/2020/test2020051601.xml')/company/shops/shop[product[local:check-price(., $factor)]] 
!
<shop id="{@id}">{
    product[local:check-price(., $factor)] 
    ! 
    <product ean="{ean}" sellingPrice="{sellingPrice}" listingPrice="{local:listing-price(.)}" />
}</shop>

https://xqueryfiddle.liberty-development.net/nc4P6y7/1或在https://xqueryfiddle.liberty-development.net/nc4P6y7/2声明上下文项。