xml XPath 中的多个条件（和运算符）
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Multiple conditions (and operator) in XPath
提问by Cédric Bignon
I have the following XML:
我有以下 XML：
<bookstore>
<books>
<book name="book1" title="Title 1" author="Author 1"/>
<book name="book2" title="Title 2" author="Author 2"/>
<book name="book3" title="Title 1" author="Author 2"/>
</books>
<myBooks>
<book name="Test1" title="Title 1" author="Author 1"/>
<book name="Test2" title="Title 2" author="Author 1"/>
<book name="Test3" title="Title 1" author="Author 2"/>
</myBooks>
</bookstore>
I want to get all nameof bookin myBooksthat have not a corresponding bookin books(title and author).
我想所有name的book在myBooks那没有一个相应book的books（标题和作者）。
So, for the example, I want to retrieve: the book "Test2"because the pair ("Title 2", "Author 1")does not exist in books.
因此，例如，我想检索：这本书，"Test2"因为这对("Title 2", "Author 1")不存在于books.
So far, I have:
到目前为止，我有：
//myBooks/book[not(@title = //books/book/@title and @author = //books/book/@author)]
But, of course, in that case, the above XPath does not work because the combination ("Title 2", "Author 1") exists (from "book2" and "book1").
但是，当然，在这种情况下，上述 XPath 不起作用，因为存在组合（“标题 2”、“作者 1”）（来自“book2”和“book1”）。
How can I apply the andoperator on the same node?
如何and在同一节点上应用运算符？
采纳答案by Ian Roberts
It depends on the version of XPath.
这取决于 XPath 的版本。
You can't do this in a single XPath 1.0 expression because it would require a structure like
您不能在单个 XPath 1.0 表达式中执行此操作，因为它需要类似的结构
/bookstore/myBooks/book[/bookstore/books/book[
@title = _outer-predicate_/@title and
@author = _outer-predicate_/@author]]/@name
i.e. you'd need to capture the book being tested by the outer predicate so you can compare it to the inner one. Pure XPath 1.0 doesn't support this, you'd have to iterate over the content of myBooksyourself (e.g. with an xsl:for-each, as you've tagged your question "xslt").
即，您需要捕获由外部谓词测试的书，以便您可以将其与内部谓词进行比较。Pure XPath 1.0 不支持此功能，您必须遍历myBooks自己的内容（例如，使用xsl:for-each，因为您已将问题标记为“xslt”）。
In XPath 2.0 you cando it in one expression with an explicit quantifier
在 XPath 2.0 中，您可以在一个带有显式量词的表达式中完成
/bookstore/myBooks/book[not(some $book in /bookstore/books/book satisfies
($book/@author = @author and $book/@title = @title))]/@name
回答by alecxe
You can concatenate attribute values using concat()and compare them:
您可以使用concat()并比较它们来连接属性值：
//myBooks/book[not(concat(@*[name() = "title" or name() = "author"], ",") = concat(//books/book/@*[name() = "title" or name() = "author"], ","))]
For every bookin myBookit gets the concatenation of titleand authorattributes and compares it with the same concatenation for every bookin books.
For each bookin myBookit 获得title和author属性的串联，并将它与每个bookin的相同串联进行比较books。
Demo (using xmllint):
演示（使用xmllint）：
$ xmllint input.xml --xpath '//myBooks/book[not(concat(@*[name() = "title" or name() = "author"], ",") = concat(//books/book/@*[name() = "title" or name() = "author"], ","))]'
<book name="Test2" title="Title 2" author="Author 1"/>
回答by Martin Honnen
Assuming XSLT I would define a key <xsl:key name="book" match="books/book" use="concat(@title, '|', @author)"/>and then in the predicate you can check [not(key('book', concat(@title, '|', @author)))].
假设 XSLT 我会定义一个键<xsl:key name="book" match="books/book" use="concat(@title, '|', @author)"/>，然后在谓词中你可以检查[not(key('book', concat(@title, '|', @author)))].
