在 XPath 1.0 中选择多个节点下属性的最小值/最大值 [英] Selecting the min/max value of an attribute under multiple nodes in XPath 1.0

问题描述

考虑以下 XML 结构:

Consider the following XML structure:

<a>
<b>
    <c>
        <d x="1"/>
        <d x="2"/>
        <d x="3"/>
        <d x="3"/>
        <d x="4"/>
    </c>
</b>
<b>
    <c>
        <d x="1"/>
        <d x="1"/>
        <d x="2"/>
        <d x="3"/>
        <d x="4"/>
        <d x="5"/>
        <d x="5"/>
    </c>
</b>
<b>
    <c>
        <d x="1"/>
        <d x="2"/>
        <d x="3"/>
        <d x="3"/>
        <d x="4"/>
        <d x="5"/>
        <d x="5"/>
    </c>
</b>

我想要一个 XPath 1.0 语句来给我@x 的最小值和最大值?到目前为止，我有以下最低要求:

I'd like a XPath 1.0 statement to give me the minimum and maximum values of @x? So far I have the following for the minimum:

//a/b/c/d[not(preceding-sibling::d/@x <= @x) and not(following-sibling::d/@x <= @x)]/@x

//a/b/c/d[not(preceding-sibling::d/@x <= @x) and not(following-sibling::d/@x <= @x)]/@x

很接近，但没有雪茄:-(

which is close, but no cigar :-(

非常感谢任何帮助！

谢谢，J

推荐答案

要获取最大值，请查找没有较小值的所有属性值.如果有多个结果，取第一个 - 它们必须相等.

To fetch the maximum value, look for all attribute values for which there are not smaller ones. If there are multiple results, take the first one - they must be equal.

(//@x[not(. < //@x)])[1]

对于最小值，只需将 < 替换为 >.

For the minimum value, just replace < by >.

出于完整性原因:如果您的 XPath 引擎支持 XPath 2.0(或更好)，只需使用 max(//@x) 尊重 min(//@x) 这可能会更快，更易读.

For completeness reasons: if your XPath engine supports XPath 2.0 (or better), just use max(//@x) respecting min(//@x) which will probably be faster and more readable.

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