Question

When getting values out of xml attributes, using the xquery value operator, missing attributes are returned as null. Is there a way to do the same thing without resorting to CASE WHEN N.exists('path')=0 THEN NULL ELSE n.value('path') END?

This SQL:

DECLARE @val xml
SET @val = '<records>
  <record attrval="attrval">
    <stringvalue>some value</stringvalue>
    <intvalue>1</intvalue>
  </record>
  <record>
    <intvalue>1</intvalue>
  </record>
  <record>
    <stringvalue>another value</stringvalue>
  </record>
</records>'

SELECT N.query('stringvalue').value('/', 'varchar(100)') AS stringvalue,
       N.query('intvalue').value('/', 'int') AS intvalue,
       N.value('@attrval', 'varchar(100)') AS attrval
FROM @val.nodes('//record') as T(N)

Results in:

[stringvalue]       [intvalue]  [attrval]
some value          1           attrval
                    1           NULL
another value       0           NULL

And I would like to get:

[stringvalue]       [intvalue]  [attrval]
some value          1           attrval
NULL                1           NULL
another value       NULL        NULL

Without doing:

SELECT CASE WHEN N.exists('stringvalue')=1 THEN N.query('stringvalue').value('/', 'varchar(100)') ELSE NULL END AS stringvalue,
       CASE WHEN N.exists('intvalue')=1 THEN N.query('intvalue').value('/', 'int') ELSE NULL END AS intvalue,
       N.value('@attrval', 'varchar(100)') AS attrval
FROM @val.nodes('//record') as T(N)

Note that in this case I can’t just use attribute values because there is a limit on the length of the attributes imposed by SQL Server and some of my data exceeds that.

Also, there is a related question but the answer is not applicable because I need to distinguish between empty and missing: SQL Server xQuery return NULL instead of empty

Answer 1

SELECT N.value('stringvalue[1]', 'varchar(100)') AS stringvalue,
       N.value('intvalue[1]', 'int') AS intvalue,
       N.value('@attrval', 'varchar(100)') AS attrval
FROM @val.nodes('//record') as T(N)