Xquery 如何计算具有相同日期的子项的节点数

下面是Xml结构。我必须清点同一日期的安装情况，并列出它们。因此，我必须按InstallDate查找count并在XQuery中返回，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>

个人计算机
Y
2020-10-01T00:00:00:000Z
个人计算机
Y
2020-10-01T00:00:00:000Z
个人计算机
Y
2020-10-02T00:00:00:000Z
个人计算机
Y
2020-10-02T00:00:00:000Z
个人计算机
Y
2020-10-02T00:00:00:000Z

即使在XQuery 1.0中也非常简单

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,', ')

---

即使在XQuery1.0中也非常简单

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,', ')

---

如果您希望在MarkLogic server中按日期分组、计数和列出

安装

，请参阅下面的

MarkLogic XQuery方言

：

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> 

---

如果您希望在MarkLogic server中按日期分组、计数和列出

安装

，请参阅下面的

MarkLogic XQuery方言

：

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>