如何使用 XQuery 獲取記錄數

Question

我有包含書籍記錄的“Library.xml”文件

<?xml version="1.0" encoding="UTF-8"?>
<library>
    <book>
        <title>DBMS</title>
        <author>Korth</author>
        <publisher>Pragati</publisher>
        <price>500</price>
    </book>

    <book>
        <title>C Programming</title>
        <author>Balguruswami</author>
        <publisher>Vision</publisher>
        <price>1250</price>
    </book>

    <book>
        <title>DBMS</title>
        <author>Balguruswami</author>
        <publisher>Vision</publisher>
        <price>1300</price>
    </book>

    <book>
        <title>DBMS</title>
        <author>Ramakrishna</author>
        <publisher>Nirali</publisher>
        <price>350</price>
    </book>

    <book>
        <title>C++</title>
        <author>E Balguruswami</author>
        <publisher>Techmax</publisher>
        <price>350</price>
    </book>

</library>

如何僅使用XQuery - FLOWER獲得 DBMS 書籍的數量？ 我試過這個：

let $books := (doc("LibraryXML.xml")/library/book)

    return <result>
    {
        for $x in $books
        where $x/title = "DBMS"
        return count($x)
    }
    </result>

根據library.xml答案應該是 3。但我得到的是：

<?xml version="1.0" encoding="UTF-8"?>
<result>1 1 1</result>

Answer 1

要在 XQuery 3.0 中做到這一點，不需要包含所有子句的完整 FLWOR 表達式。

一探究竟。

XQuery

let $library := doc("e:\Temp\LibraryXML.xml")/library/book[title='DBMS']
return <result>{count($library)}</result>

Output

<result>3</result>