By default, elements and attributes that contain NULL values are omitted from the result. This behavior is controlled by the for_xml_null_treatment option.

Consider an entry in the Customers table that contains a NULL company name.

INSERT INTO 
      Customers( ID, Surname, GivenName, Street, City, Phone) 
VALUES (100,'Robert','Michael',
       '100 Anywhere Lane','Smallville','519-555-3344');

If you execute the following query with the for_xml_null_treatment option set to Omit (the default), then no attribute is generated for a NULL column value.

SELECT ID, GivenName, Surname, CompanyName
FROM Customers
WHERE GivenName LIKE 'Michael%'
ORDER BY ID
FOR XML RAW;

In this case, no CompanyName attribute is generated for Michael Robert.

<row ID="100" GivenName="Michael" Surname="Robert"/>
<row ID="101" GivenName="Michaels" Surname="Devlin" CompanyName="The Power Group"/>
<row ID="110" GivenName="Michael" Surname="Agliori" CompanyName="The Pep Squad"/>

If the for_xml_null_treatment option is set to Empty, then an empty attribute is included in the result:

<row ID="100" GivenName="Michael" Surname="Robert" CompanyName=""/>
<row ID="101" GivenName="Michaels" Surname="Devlin" CompanyName="The Power Group"/>
<row ID="110" GivenName="Michael" Surname="Agliori" CompanyName="The Pep Squad"/>

In this case, an empty CompanyName attribute is generated for Michael Robert.

For information about the for_xml_null_treatment option, see for_xml_null_treatment option.