xquery - 如何在 Xquery 中对具有相同代码属性的多项进行求和？

Question

我在 Xquery 中进行练习时遇到问题。逻辑:

• 获取购买次数超过5次的商品名称及其单价

这是xml文件的结构:

<shop>
    <products>
        <product code="P02">
            <name>Hard disk SSD</name>
            <price>320</price>
        </product>
        <product code="P05">
            <name>Keyboard</name>
            <price>30</price>
        </product>
        <product code="P06">
            <name>NAS</name>
            <price>400</price>
        </product>
    </products>
    <purchases>
        <quantity product="P02" client="U300111">5</quantity>
        <quantity product="P05" client="U300111">3</quantity>
        <quantity product="P05" client="U120711">1</quantity>
        <quantity product="P02" client="U120711">7</quantity>
        <quantity product="P06" client="U030512">1</quantity>
        <quantity product="P06" client="U120712">3</quantity>
        <quantity product="P02" client="U120712">1</quantity>
    </purchases>
</shop>

我现在已经这样做了:

for $x in doc("LMSGI06")/shop/purchases/quantity, $y in doc ("LMSGI06")/shop/products/product
let $z := sum($x)
where $x/@product = $y/@code and $z > 5
return  
<product>
    {$y/name}
    {$y/price}
    <sales>{$z}</sales>
</producto>

这就是结果:

<product>
    <name>Hard disk SSD</name>
    <price>320</price>
    <sales>7</sales>
</product>

我正在尝试添加产品数量，但无法添加具有相同产品代码的产品，然后在 where 子句中按购买次数超过的产品进行过滤5次。有人知道我该怎么做吗？非常感谢。

结果应该是:

<product>
    <name>Hard disk SSD</name>
    <price>320</price>
    <sales>13</sales>
</product>

Answer 1

如果您的 XQuery 版本支持，请使用group by:

for $product in /shop/products/product
let $code := $product/@code
group by $code
let $sum := sum(/shop/purchases/quantity[@product=$code])
where $sum > 5
return 
<product>
    {$product/name}
    {$product/price}
    <sales>{$sum}</sales>
</product>

或者使用distinct-values()来模拟相同的逻辑，否则:

for $code in distinct-values(/shop/products/product/@code)
let $product := /shop/products/product[@code=$code]
let $qty := /shop/purchases/quantity[@product=$code]
let $sum := sum($qty)
where $sum > 5
return  
<product>
    {$product/name}
    {$product/price}
    <sales>{$sum}</sales>
</product>

demo