Selecting null value from XML in SQL Server

Question

I'm trying to select from XML that has a null as one of the attributes. Instead of returning a null, it returns a 0. What am I doing wrong?
See code below to replicate:

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

This returns the same thing:

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)

Thanks in advance.

Answer 1

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

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

This will select null. By the way author code has a typo

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

instance is misspelled as instace

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

Working version of author code

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)

Answer 2

I would sugest this approach:

DECLARE @a XML = '<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
        .value('./Property1[not(./@*[local-name()="nil"] = "true")][1]', 'int') as Property1,
    ParamValues.TaskChainerTask
        .value('./Property2[not(./@*[local-name()="nil"] = "true")][1]', 'int') as Property2
FROM @a.nodes('//Element') ParamValues(TaskChainerTask)