[英]XPath filter by attribute and return distinct values
从下面我需要返回具有Category
属性的不同值列表。
<root>
<classifications>
<classification name="Category">Category One</classification>
<classification name="Sub-Category">Sub-Category One</classification>
</classifications>
<classifications>
<classification name="Category">Category Two</classification>
<classification name="Sub-Category">Sub-Category One</classification>
</classifications>
<classifications>
<classification name="Category">Category One</classification>
<classification name="Sub-Category">Sub-Category Two</classification>
</classifications>
<classifications>
<classification name="Category">Category Three</classification>
<classification name="Sub-Category">Sub-Category One</classification>
</classifications>
<classifications>
<classification name="Category">Category One</classification>
<classification name="Sub-Category">Sub-Category Two</classification>
</classifications>
<classifications>
<classification name="Category">Category Two</classification>
<classification name="Sub-Category">Sub-Category One</classification>
</classifications>
</root>
使用classifications/classification[@name="Category"]
我得到:
Category One
Category Two
Category One
Category Three
Category One
Category Two
我需要的是:
Category One
Category Two
Category Three
此 XPath 将选择不同的元素:
//classification[@name = "Category" and not(preceding::classification = .)]
或更具体的:
//classification[@name = "Category"
and not(preceding::classification[@name = "Category"] = .)
]
对于那些能够使用 XPath 2.0 及更高版本的人:
另一种可能更灵活且似乎更有效(至少在 Saxon 9.8.0 中)的替代方法是:
distinct-values(//classification[@name = 'Category'])
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