Question

我试图从表中读取一个varchar列，但是这个列实际上是Xml，因此我将该值转换为XML并尝试从那里获取值。

问题在于我总是变空。这是我的代码：

declare @Greeting xml = (select CAST(sg.Greeting as xml) from AnsService.Ans.SiteGroup sg with (nolock) where sg.SiteGroupNum = 2032)

select 
    sg.AnswerAs,
    (select xmlData.Col.value('.', 'varchar(max)') from @Greeting.nodes('//Section/Paragraph/Run') xmlData(col)) as Greeting
from AnsService.Ans.SiteGroup sg with (nolock)
where sg.SiteGroupNum = 2032

转换后的xml值为：

<Section xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xml:space="preserve>
  <Paragraph>
    <Run>Thank you for calling Intelli-tec Security Services.  This is [OpFirst] speaking, how may I help you?</Run>
  </Paragraph>
</Section>

任何人都可以帮我识别我的问题，谢谢

Answer 1

有几个缺陷：

bad habit to kick: NOLOCK everywhere
如果您向我们展示的XML已完整，则APPLY

.nodes()

在＆＃34; Section＆＃34;之前不要使用双//。这会触发深度搜索，并在XML

<Section>

您的XML定义了默认命名空间。您必须使用它或使用通配符
您应该以适当的类型存储XML。不需要演员表（例如select CAST(sg.Greeting as xml）
看起来好像这个XML存储在您正在阅读其余内容的同一个表中。（可能）没有必要先将其读入变量

试试这个：

DECLARE @Greeting XML=
N'<Section xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xml:space="preserve">
  <Paragraph>
    <Run>Thank you for calling Intelli-tec Security Services.  This is [OpFirst] speaking, how may I help you?</Run>
  </Paragraph>
</Section>';

--declared namespace
SELECT
    @Greeting.value('declare namespace ns1="http://schemas.microsoft.com/winfx/2006/xaml/presentation";
                     (/ns1:Section/ns1:Paragraph/ns1:Run/text())[1]','nvarchar(max)') Greeting;

--predefined namespace
WITH XMLNAMESPACES(DEFAULT 'http://schemas.microsoft.com/winfx/2006/xaml/presentation')
SELECT
    @Greeting.value('(/Section/Paragraph/Run/text())[1]','nvarchar(max)') Greeting;

--no namespace but wildcards
SELECT
    @Greeting.value('(/*:Section/*:Paragraph/*:Run/text())[1]','nvarchar(max)') Greeting;

如果我的魔法水晶球工作正常，你需要这样的东西

select 
    sg.AnswerAs,
    CAST(sg.Greeting AS XML).value('declare namespace ns1="http://schemas.microsoft.com/winfx/2006/xaml/presentation";
                                    (/ns1:Section/ns1:Paragraph/ns1:Run/text())[1]','nvarchar(max)') AS Greeting
from AnsService.Ans.SiteGroup sg with (nolock)
where sg.SiteGroupNum = 2032

获取null尝试读取XML列值SQL

1 个答案: