如何计算具有相同日期的子项的节点

问题描述

我有下面这样的Xml结构。我将必须计算同一日期的安装并列出它们。因此，我将必须通过InstallDate查找计数并返回XQuery以便在Marklogic查询中使用。

<PcDetail>
<Installations>
    <Installation>
        <Type>pc</Type>
        <purchased>Y</purchased>
        <InstallDate>2020-10-01T00:00:00:000Z</InstallDate>
    </Installation>
    <Installation>
        <Type>pc</Type>
        <purchased>Y</purchased>
        <InstallDate>2020-10-01T00:00:00:000Z</InstallDate>
    </Installation>
    <Installation>
        <Type>pc</Type>
        <purchased>Y</purchased>
        <InstallDate>2020-10-02T00:00:00:000Z</InstallDate>
    </Installation>
    <Installation>
        <Type>pc</Type>
        <purchased>Y</purchased>
        <InstallDate>2020-10-02T00:00:00:000Z</InstallDate>
    </Installation>
    <Installation>
        <Type>pc</Type>
        <purchased>Y</purchased>
        <InstallDate>2020-10-02T00:00:00:000Z</InstallDate>
    </Installation>
</Installations>

解决方法

如果您希望在MarkLogic服务器中按日期分组，计数和列出Installation，请参见以下MarkLogic XQuery dialect：

for $d in distinct-values(doc()//InstallDate)
let $i := doc()//Installation[InstallDate = $d]
order by $d
return <Installations Date="{$d}" Count="{count($i)}">
{
for $install in $i
return $install
}</Installations> 

在事务驱动的环境中，您应该使用MarkLogic性能搜索引擎：

for $vt in cts:value-tuples(
    (cts:element-reference(xs:QName( 'InstallDate'))
    ),("item-frequency")
    )
return "Installation on " || $vt[1] || " total count: " || cts:frequency($vt) 

,

即使在XQuery 1.0中，它也非常简单

let $installations := $xml/PcDetail/Installations/Installation

for $date in fn:distinct-values($installations/InstallDate)
let $installationsOnDate := $installations[InstallDate = $date]
let $c := count($installationsOnDate)
return $date || ':' || $c || ':' || string-join($installationsOnDate/type,',')