从 SQL Server 中的 XML 选择空值

我正在尝试从具有 null 作为属性之一的 XML 中进行选择。它没有返回 null，而是返回 0。我做错了什么？
请参阅下面的代码进行复制：

declare @a xml
select @a = '<TestSet xmlns:xsi="http://www.w3.org/2001/XMLSchema-instace">
  <Element>
    <Property1>1</Property1>
    <Property2>1</Property2>
  </Element>
  <Element>
    <Property1 xsi:nil="true" />
    <Property2>2</Property2>
  </Element>
  <Element>
    <Property1>3</Property1>
    <Property2>3</Property2>
  </Element>
</TestSet>'

 select ParamValues.TaskChainerTask.query('Property1').value('.','int') as Property1,
        ParamValues.TaskChainerTask.query('Property2').value('.','int') as Property2
   from @a.nodes('(/TestSet/Element)') as ParamValues(TaskChainerTask)

returns:

Property1   Property2
1           1
0           2
3           3

这返回同样的东西：

declare @a xml
select @a = '<TestSet xmlns:xsi="http://www.w3.org/2001/XMLSchema-instace">
  <Element>
    <Property1>1</Property1>
    <Property2>1</Property2>
  </Element>
  <Element>
    <Property1 xsi:nil="true" />
    <Property2>2</Property2>
  </Element>
  <Element>
    <Property1>3</Property1>
    <Property2>3</Property2>
  </Element>
</TestSet>'

 select ParamValues.TaskChainerTask.query('Property1').value('.','int') as Property1,
        ParamValues.TaskChainerTask.query('Property2').value('.','int') as Property2
   from @a.nodes('(/TestSet/Element)') as ParamValues(TaskChainerTask)

提前致谢。

http://go4answers.webhost4life.com/Example/include-null-columns-empty-elements-125474.aspx http://go4answers.webhost4life.com/Example/including-null-columns-empty-elements-125474.aspx

[not(@xsi:nil = "true")]

这将选择空。顺便说一句，作者代码有一个拼写错误

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instace"

实例被错误拼写为实例

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

作者代码的工作版本

declare @a xml
            select @a = '<TestSet xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
              <Element>
                <Property1>1</Property1>
                <Property2>1</Property2>
              </Element>
              <Element>
                <Property1 xsi:nil="true" />
                <Property2>2</Property2>
              </Element>
              <Element>
                <Property1>3</Property1>
                <Property2>3</Property2>
              </Element>
            </TestSet>'

             select ParamValues.TaskChainerTask.value('./Property1[1][not(@xsi:nil = "true")]','int') as Property1,
                    ParamValues.TaskChainerTask.value('./Property2[1][not(@xsi:nil = "true")]','int') as Property2
               from @a.nodes('(/TestSet/Element)') as ParamValues(TaskChainerTask)