使用"group“和嵌套FLWOR

Question

我很难理解如何使用嵌套的FLWOR表达式和group。这里有一个XML文档示例，以及我想要做的事情。

 <review>
 <critic name="Critic1">
 <book>
    <name>ABC</name>
    <rating>6</rating>
 </book>
 <book>
    <name>Monsters</name>
    <rating>2</rating>
 </book>
 <book>
    <name>Spring Poems</name>
    <rating>5</rating>
 </book>
 </critic>
 <critic name="Critic2">
 <book>
    <name>ABC</name>
    <rating>2</rating>
 </book>
 <book>
    <name>Cooking101</name>
    <rating>7</rating>
 </book>
 <book>
    <name>Aliens?</name>
    <rating>10</rating>
 </book>
 </critic>
 </review>

基本上，我要做的是按每本书的名字把数据分组，然后在每本书下面展示每一位评论它的评论家，以及他们给那本书的分数。

到目前为止，我的疑问是

 for $books in doc("reviews.xml")/review/critic/book
 let $critics := doc("reviews.xml")/review/critic
 let $d := $books/name
 group by $d
 order by $d
 return <book name="{$d}">{
     for $hasReview in $critics
     where $critics/book/name = $d
     group by $n := $d
     return <critic name="{$critics/@name}" rating="
            {$critics/book[name=$d]/rating}"/>

     }</book>

此查询的输出如下所示

 <book name ="ABC">
     <critic name = "Critic1 Critic2" rating="6 2"/>
 </book>
 <book name ="Monsters">
     <critic name = "Critic1 Critic2" rating="2"/>
 </book>
 <book name ="Spring Poems">
     <critic name = "Critic1 Critic2" rating="5"/>
 </book>
 <book name ="Cooking101">
     <critic name = "Critic1 Critic2" rating="7"/>
 </book>
 <book name ="Aliens">
     <critic name = "Critic1 Critic2" rating="10"/>
 </book>

我试图获得的输出类似于以下内容：

 <book name ="ABC">
     <critic name = "Critic1" rating="6"/>
     <critic name = "Critic2" rating="2"/>
 </book>
 <book name ="Monsters">
     <critic name = "Critic1" rating="2"/>
 </book>
 <book name ="Spring Poems">
     <critic name = "Critic1" rating="5"/>
 </book>
 <book name ="Cooking101">
     <critic name = "Critic2" rating="7"/>
 </book>
 <book name ="Aliens">
     <critic name = "Critic2" rating="10"/>
 </book>

Answer 1

我还没有使用组，因为我从未使用过任何支持它的软件。所以我想这样说：

for $bookName in distinct-values(doc("reviews.xml")/review/critic/book/name)
order by $bookName
return <book name="{$bookName}">{
    for $critic in doc("reviews.xml")/review/critic/book[name eq $bookName]
    return <critic name="{$critic/../@name}" rating="{$critic/rating}" />
}</book>

在对样本数据进行测试时，我得到了以下结果：

<book name="ABC">
  <critic name="Critic1" rating="6"/>
  <critic name="Critic2" rating="2"/>
</book>
<book name="Aliens?">
  <critic name="Critic2" rating="10"/>
</book>
<book name="Cooking101">
  <critic name="Critic2" rating="7"/>
</book>
<book name="Monsters">
  <critic name="Critic1" rating="2"/>
</book>
<book name="Spring Poems">
  <critic name="Critic1" rating="5"/>
</book>

你甚至不确定你在这里找的是什么。通过查看您的输出，它似乎奇怪地将两个评论家节点的属性合并到一个属性中(这可能正是它应该做的事情，但不是您所需要的)。