如何使用XQuery以逗号分隔的格式基于多个条件提取特定的XML记录？

输入文件：

<?xml version="1.0" encoding="UTF-8"?> 
        <books>
            <book id="6636551">
                <master_information>
                    <book_xref>
                        <xref type="Fiction" type_id="1">72771KAM3</xref>
                        <xref type="Non_Fiction" type_id="2">US72771KAM36</xref>
                    </book_xref>
                </master_information>
                <book_details>
                    <price>24.95</price>
                    <publish_date>2000-10-01</publish_date>
                    <description>An in-depth look at creating applications with XML.</description>
                </book_details>
                <global_information>
                    <ratings>
                        <rating agency="ABC Agency" type="Author Rating">A++</rating>
                        <rating agency="DEF Agency" type="Author Rating">A+</rating>
                        <rating agency="DEF Agency" type="Book Rating">A</rating>
                    </ratings>
                </global_information>
                <country_info>
                    <country_code>US</country_code>
                </country_info>
            </book>
            <book id="119818569">
                <master_information>
                    <book_xref>
                        <xref type="Fiction" type_id="1">070185UL5</xref>
                        <xref type="Non_Fiction" type_id="2">US070185UL50</xref>
                    </book_xref>
                </master_information>
                <book_details>
                    <price>19.25</price>
                    <publish_date>2002-11-01</publish_date>
                    <description>A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.</description>
                </book_details>
                <global_information>
                    <ratings>
                        <rating agency="ABC Agency" type="Author Rating">A+</rating>
                        <rating agency="ABC Agency" type="Book Rating">A</rating>
                        <rating agency="DEF Agency" type="Author Rating">A</rating>
                        <rating agency="DEF Agency" type="Book Rating">B+</rating>
                    </ratings>
                </global_information>
                <country_info>
                    <country_code>CA</country_code>
                </country_info>
            </book>
            <book id="119818568">
                <master_information>
                    <book_xref>
                        <xref type="Fiction" type_id="1">070185UK7</xref>
                        <xref type="Non_Fiction" type_id="2">US070185UK77</xref>
                    </book_xref>
                </master_information>
                <book_details>
                    <price>5.95</price>
                    <publish_date>2004-05-01</publish_date>
                    <description>After the collapse of a nanotechnology society in England, the young survivors lay the foundation for a new society.</description>
                </book_details>
                <global_information>
                    <ratings>
                        <rating agency="ABC Agency" type="Author Rating">A+</rating>
                        <rating agency="ABC Agency" type="Book Rating">A+</rating>
                        <rating agency="DEF Agency" type="Author Rating">B++</rating>
                        <rating agency="DEF Agency" type="Book Rating">A+</rating>
                    </ratings>
                </global_information>
                <country_info>
                    <country_code>UK</country_code>
                </country_info>
            </book>
            <book id="119818567">
                <master_information>
                    <book_xref>
                        <xref type="Fiction" type_id="1">070185UJ0</xref>
                        <xref type="Non_Fiction" type_id="2">US070185UJ05</xref>
                    </book_xref>
                </master_information>
                <book_details>
                    <price>4.95</price>
                    <publish_date>2000-09-02</publish_date>
                    <description>When Carla meets Paul at an ornithology conference, tempers fly as feathers get ruffled.</description>
                </book_details>
                <global_information>
                    <ratings>
                        <rating agency="ABC Agency" type="Author Rating">B+</rating>
                        <rating agency="ABC Agency" type="Book Rating">A+</rating>
                        <rating agency="DEF Agency" type="Author Rating">B++</rating>
                        <rating agency="DEF Agency" type="Book Rating">A+</rating>
                    </ratings>
                </global_information>
                <country_info>
                    <country_code>US</country_code>
                </country_info>
            </book>
        </books>

预期产出为：

book_id, xref_type, xref, country, desc, rating_agency, rating_type, rating
6636551,Fiction,72771KAM3,US,An in-depth look at creating applications with XML.,DEF Agency,Author Rating,A+
6636551,Non_Fiction,US72771KAM36,US,An in-depth look at creating applications with XML.,DEF Agency,Author Rating,A+
119818569,Fiction,070185UL5,CA,A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.,ABC Agency,Author Rating,A+
119818569,Non_Fiction,US070185UL50,CA,A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.,ABC Agency,Author Rating,A+
etc.

因为我没有对外部参照类型进行过滤，所以应该在单独的行中显示它们，所以我希望book_ID会重复，但事实并非如此。生成的输出如下所示：

book_id, xref_type, xref, country, desc, rating_agency, rating_type, rating
6636551,Fiction,Non_Fiction,72771KAM3,US72771KAM36,US,An in-depth look at creating applications with XML.,DEF Agency,Author Rating,A+
119818569,Fiction,Non_Fiction,070185UL5,US070185UL50,CA,A former architect battles corporate zombies, an evil sorceress, and her own childhood to become queen of the world.,ABC Agency,Author Rating,A+

当我对xref_type=“Fiction”进行过滤时，我必须同时对xref/@type和xref进行过滤。这是可行的，但有更好的方法吗

基本上，我的问题可以分为三个小问题：

我怎样才能在列表中列出“虚构”和“非虚构”项目 同一给定图书id的单独行

有没有更好的方法来编写此代码的条件

当特定条件缺少数据时，如何以输出空白值的方式写入条件？这是自动完成的吗

我感谢你的帮助

在计算XPath表达式

祖先：：book//book_xref/xref/@type

时，上下文是单个

评级

元素，结果是

类型=“…”

属性的序列。因此，当您组装CSV行时，祖先

book

元素的所有类型的图书引用都被视为一个值（可以是一个项目序列）

如果要将每个项目分离到其单独的CSV行中，则必须使用例如

for

循环对序列进行递归迭代。我使用

let

和循环覆盖所有

xref

s将

book

绑定到一个变量：

string-join(
  (
    'book_id, xref_type, xref, country, desc, rating_agency, rating_type, rating',
    for $rating in //book//global_information/ratings/rating[@type='Author Rating' and .=('A+','B++')]
    let $book := $rating/ancestor::book
    for $xref in $book//xref
    return (
      string-join(
        (
          $book/@id,
          $xref/@type,
          $xref/text(),
          $book//country_info/country_code,
          $book//book_details/description/text(),
          $rating/@agency,
          $rating/@type,
          $rating/text()
        ),
        ','
      )
    )
  ),
  '
'
)

如果要避免向后轴（有时可能有点笨拙），也可以先迭代

书籍

s，然后迭代您感兴趣的

评级

s：

string-join(
  (
    'book_id, xref_type, xref, country, desc, rating_agency, rating_type, rating',
    for $book in //book
    for $rating in $book/global_information/ratings/rating[@type='Author Rating' and .=('A+','B++')]
    for $xref in $book//xref
    [...]

---

现在这很有道理。这太酷了！每次我在这里问问题，我都会学到更多。谢谢！非常感谢你的解释。可能是一个愚蠢的后续问题，但我如何才能过滤国家价值观？我像

$book//country\u info/country\u code[数据[.='US'，'UK']].

那样写它，但这不起作用。我也试过不用“数据”。直接过滤元素数据的正确方法是什么？第一次尝试时有几个问题。首先，如果编写

$foo[x=$bar，$baz]

，则在谓词内部创建一个包含两部分的序列

x=$bar

，和

$baz

。如果要匹配序列中的某个元素，则必须使用parens构建该序列：

$foo[x=（$bar，$baz）]

。其次，

data

不是XQuery中的关键字。您可能指的是函数

data（）

，它返回上下文值的原子化（即非XML）内容。因此，一个解决方案是

$book//country\u info/country\u code[data（）[.=（'US'，'UK'）]]

，这很有意义$book//country\u info/country\u code[data（）[.=（'US'，'UK'）]]以某种方式仅从输出中删除非英国或美国的所有国家/地区值-假设目标是过滤输出以包含仅与英国或美国相关的记录。你会怎么做？我尝试创建一个新的$book1，就像$book一样，但是包含国家代码的过滤器，但是它会以某种方式输出相同的图书id，并且两个国家代码在不同的行上。它正在增加价值！

string-join(
  (
    'book_id, xref_type, xref, country, desc, rating_agency, rating_type, rating',
    for $book in //book
    for $rating in $book/global_information/ratings/rating[@type='Author Rating' and .=('A+','B++')]
    for $xref in $book//xref
    [...]