为什么Xquery给我变量一个错误？ 一世

Question

I am very new to XML and XQUERY and am having a terrible time trying to validate , what is probably incredibly easy code. The validator keeps telling me that I have an unknown function or expression but seems to stop around my variable. Can anyone help? I'm sure this is an incredibly easy question but I have been banging my head against the wall trying to figure out what I am doing wrong. Here is the XML:

<PurchaseOrders>
  <PurchaseOrder PurchaseOrderNumber="99503" OrderDate="1999-10-20">
    <Address Type="Shipping">
      <Name>Ellen Adams</Name>
    </Address>
    <Address Type="Billing">
      <Name>Tai Yee</Name>
    </Address>
    <Items>
      <Item PartNumber="872-AA">
        <ProductName>Lawnmower</ProductName>
      </Item>
      <Item PartNumber="926-AA">
        <ProductName>Baby Monitor</ProductName>
      </Item>
    </Items>
  </PurchaseOrder>
 </PurchaseOrders>

my Xquery:

for $x in doc/PurchaseOrders/PurchaseOrder
    let $z := $x/Items/Item
    let$n := count($z)
    where $x/Address[@Type = 'Shipping'] order by $x/Name ascending
    return <Orders><Order><Name>{$x/Name}</Name><NoProducts>$n</NoProducts></Order></Orders>

Expected output:

<Orders>
  <Order>
    <name>Ellen Adams</name>
    <noProducts>2</noProducts>
  </Order>
 </Orders>

What did I do wrong? I know this is basic but I would love to learn! Thanks!

Answer 1

I can't speak to what you did wrong (since the error provided in the question was insufficiently precise, and when running that same query myself, I received an empty result, but also no errors), but I can provide a query that generates the output you expect.

declare context item := document {
  <PurchaseOrders>
    <PurchaseOrder PurchaseOrderNumber="99503" OrderDate="1999-10-20">
      <Address Type="Shipping">
        <Name>Ellen Adams</Name>
      </Address>
      <Address Type="Billing">
        <Name>Tai Yee</Name>
      </Address>
      <Items>
        <Item PartNumber="872-AA">
          <ProductName>Lawnmower</ProductName>
        </Item>
        <Item PartNumber="926-AA">
          <ProductName>Baby Monitor</ProductName>
        </Item>
      </Items>
    </PurchaseOrder>
  </PurchaseOrders>
};

<Orders>{
for $purchaseOrder in /PurchaseOrders/PurchaseOrder[Address/@Type='Shipping']
    let $shippingAddress := $purchaseOrder/Address[@Type='Shipping']
    let $items := $purchaseOrder/Items/Item
    let $itemCount := count($items)
    order by $shippingAddress/Name ascending
    return <Order>
             <Name>{$shippingAddress/Name}</Name>
             <PONum>{string($purchaseOrder/@PurchaseOrderNumber)}</PONum>
             <NoProducts>{$itemCount}</NoProducts>
           </Order>
}</Orders>

Note that whereas previously $x pointed to a purchase order, here the key is a shipping address -- important, because otherwise your $x/Name found no data.