如何使用 XPATH 从 XML 文档中选择不同的值？
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How to select distinct values from XML document using XPATH?
提问by Alex
How can I select only distinct elements for the XML document using XPATH?I've tried to use the 'distinct-values' function but it didn't work for some reason..
如何使用 XPATH 只为 XML 文档选择不同的元素？我尝试使用“distinct-values”函数，但由于某种原因它不起作用。
The XML is similar to the following:
XML 类似于以下内容：
<catalog>
<product>
<size>12</size>
<price>1000</price>
<rating>1</rating>
</product>
<product>
<size>10</size>
<price>1000</price>
<rating>1</rating>
<year>2010</year>
</product>
</catalog>
So what I want to get is the list of distinct children of all the product elements.In the given example it would be - size,price,rating,year My xpath was something like : distinct-values(catalog/product/*)
所以我想要的是所有产品元素的不同子元素的列表。在给定的示例中，它是 - 大小、价格、评级、年份我的 xpath 类似于：distinct-values(catalog/product/*)
回答by Dimitre Novatchev
In XPath 2.0:
在 XPath 2.0 中：
distinct-values(/*/*/*/name(.))
In XPath 1.0 this cannot be produced with a single XPath expression.
在 XPath 1.0 中，这不能用单个 XPath 表达式生成。
Using XSLT 1.0:
使用 XSLT 1.0：
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:template match="/">
<xsl:for-each select=
"/*/*/*[not(../following::*/*
[not(name() = name(current()))]
)
]">
<xsl:value-of select="concat(name(), ' ')"/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the provided XML document, the wanted result is produced:
当此转换应用于提供的 XML 文档时，会产生所需的结果：
size price rating year
A more efficient XSLT 1.0 transformation, using keys:
更高效的 XSLT 1.0 转换，使用 keys：
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:key name="kpchildByName"
match="product/*" use="name()"/>
<xsl:template match="/">
<xsl:for-each select=
"/*/*/*
[generate-id()
=
generate-id(key('kpchildByName', name())[1])
]">
<xsl:value-of select="concat(name(), ' ')"/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
回答by 341008
distinct-values()is available in XPath 2.0. Are you using that?
distinct-values()在 XPath 2.0 中可用。你用那个？
If distinct-values()is not available, the standard way of getting distinct values is to use not(@result = preceding:: @result)to get unique @result. It will give you the first occurrence only.
如果distinct-values()不可用，则获取不同值的标准方法是使用not(@result = preceding:: @result)获取唯一的 @result。它只会给你第一次出现。
回答by Chris Wallace
You need the distinct values of the element names - something like:
您需要元素名称的不同值 - 例如：
distinct-values($catalog/product/*/name(.))
