xml 如何计算节点中的不同值？
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How to count distinct values in a node?
提问by Daniel Silveira
How to count distinct values in a node in XSLT?
如何计算 XSLT 节点中的不同值？
Example: I want to count the number of existing countries in Country nodes, in this case, it would be 3.
示例：我想计算 Country 节点中现有国家的数量，在这种情况下，它将是 3。
<Artists_by_Countries>
<Artist_by_Country>
<Location_ID>62</Location_ID>
<Artist_ID>212</Artist_ID>
<Country>Argentina</Country>
</Artist_by_Country>
<Artist_by_Country>
<Location_ID>4</Location_ID>
<Artist_ID>108</Artist_ID>
<Country>Australia</Country>
</Artist_by_Country>
<Artist_by_Country>
<Location_ID>4</Location_ID>
<Artist_ID>111</Artist_ID>
<Country>Australia</Country>
</Artist_by_Country>
<Artist_by_Country>
<Location_ID>12</Location_ID>
<Artist_ID>78</Artist_ID>
<Country>Germany</Country>
</Artist_by_Country>
</Artists_by_Countries>
回答by JeniT
If you have a large document, you probably want to use the "Muenchian Method", which is usually used for grouping, to identify the distinct nodes. Declare a key that indexes the things you want to count by the values that are distinct:
如果您有一个大文档，您可能想使用通常用于分组的“Muenchian 方法”来识别不同的节点。声明一个键，用不同的值索引你想要计数的东西：
<xsl:key name="artists-by-country" match="Artist_by_Country" use="Country" />
Then you can get the <Artist_by_Country>elements that have distinct countries using:
然后您可以使用以下方法获取<Artist_by_Country>具有不同国家/地区的元素：
/Artists_by_Countries
/Artist_by_Country
[generate-id(.) =
generate-id(key('artists-by-country', Country)[1])]
and you can count them by wrapping that in a call to the count()function.
您可以通过将其包装在对count()函数的调用中来计算它们。
Of course in XSLT 2.0, it's as simple as
当然，在 XSLT 2.0 中，它就像
count(distinct-values(/Artists_by_Countries/Artist_by_Country/Country))
回答by samjudson
In XSLT 1.0 this isn't obvious, but the following should give you an idea of the requirement:
在 XSLT 1.0 中，这并不明显，但以下内容应该能让您了解需求：
count(//Artist_by_Country[not(Location_ID=preceding-sibling::Artist_by_Country/Location_ID)]/Location_ID)
The more elements in your XML the longer this takes, as it checks every single preceding sibling of every single element.
XML 中的元素越多，所需的时间就越长，因为它会检查每个元素的每个前面的同级元素。
回答by Chris Marasti-Georg
Try something like this:
尝试这样的事情：
count(//Country[not(following::Country/text() = text())])
"Give me the count of all Country nodes without a following Country with matching text"
“给我所有国家节点的数量，没有跟随国家的匹配文本”
The interesting bit of that expression, IMO, is the followingaxis.
IMO 表达式的有趣之处在于以下轴。
You could probably also remove the first /text(), and replace the second with .
您也可以删除第一个/text()，然后将第二个替换为.
回答by Nick Allen
If you have control of the xml generation on the first occurence of a country you could add an attribute to the country node such as distinct='true' flag the country as "used" and not subsequently add the distinct attribute if you come across that country again.
如果您可以控制第一次出现某个国家/地区时的 xml 生成，则可以向国家/地区节点添加一个属性，例如 distinct='true' 将该国家/地区标记为“已使用”，如果遇到该国家/地区，则不要随后添加不同的属性再次国家。
You could then do
然后你可以做
<xsl:for-each select="Artists_by_Countries/Artist_by_Country/Country[@distinct='true']" />
