获取 XML 字段中的节点数 XQuery SQL Server 2008

Question

我正在尝试获取 XML 字段中的节点数。但我总是看到 0 结果。这是我的查询的样子。

 DECLARE @XmlTable TABLE (XmlResult XML)
INSERT INTO @XmlTable EXECUTE [dbo].usp_GetBooks @EditionId=400
--select * from  @XmlTable
SELECT
--Count number of nodes
  COUNT(*) AS BooksCount
FROM
(
SELECT XmlResult FROM @XmlTable
) AS XmlTable(XmlColumn)
CROSS APPLY XmlColumn.nodes('./books/book') XmlTableFunction(XmlColumn2);

我的 XML 看起来像：

<Version number ="1"> 
<books>
<book>
  <name> </name>
  <author></author>
</book>
<book>
  <name> </name>
  <author></author>
</book>
</books>
</Version>

Answer 1

我认为你的 XPath 表达式是错误的 - 试试这个：

DECLARE @XmlTable TABLE (XmlResult XML)

INSERT INTO @XmlTable EXECUTE [dbo].usp_GetBooks @EditionId=400

SELECT
    COUNT(*) AS BooksCount
FROM
   (SELECT XmlResult FROM @XmlTable) AS XmlTable(XmlColumn)
CROSS APPLY 
   XmlColumn.nodes('/Version/books/book') XmlTableFunction(XmlColumn2)

或者更简单：

DECLARE @XmlTable TABLE (XmlResult XML)

INSERT INTO @XmlTable EXECUTE [dbo].usp_GetBooks @EditionId=400

SELECT
    XmlResult.value('count(/Version/books/book)', 'int')
FROM
   @XmlTable

Answer 2

对我来说，您提供的 XML 模式

DECLARE @XmlTable TABLE (XmlResult XML)
INSERT INTO @XmlTable VALUES ('<books><book><title>GWTW</title></book></books>')
INSERT INTO @XmlTable VALUES ('<foo />')
INSERT INTO @XmlTable VALUES ('<books />')
SELECT
  COUNT(*) AS BooksCount
FROM
(
SELECT XmlResult FROM @XmlTable
) AS XmlTable(XmlColumn)
CROSS APPLY XmlColumn.nodes('./books/book') XmlTableFunction(XmlColumn2);

Exist 方法也非常有用。我使用 NULLIF 将 0 更改为 NULL （它是位，所以需要使用 SUM 进行 CAST）

SELECT COUNT(NULLIF(XmlResult.exist('./books/book'), 0)) FROM @XmlTable

编辑，更新后

您发布的 XML 也是错误的。

您没有正确指定根音：

DECLARE @XmlTable TABLE (XmlResult XML)
INSERT INTO @XmlTable VALUES ('
<Version number ="1"> 
<books>
<book>
  <name> </name>
  <author></author>
</book>
<book>
  <name> </name>
  <author></author>
</book>
</books>
</Version>')
SELECT
  COUNT(*)
FROM
(
SELECT XmlResult FROM @XmlTable
) AS XmlTable(XmlColumn)
CROSS APPLY XmlColumn.nodes('/Version/books/book') XmlTableFunction(XmlColumn2);

SELECT
  COUNT(*)
FROM
(
SELECT XmlResult FROM @XmlTable
) AS XmlTable(XmlColumn)
CROSS APPLY XmlColumn.nodes('*/books/book') XmlTableFunction(XmlColumn2);