null-handling-sqlxml-4-0.md

title	NULL Handling (SQLXML 4.0) | Microsoft Docs
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ms.date	03/17/2017
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helpviewer_keywords	updg:nullvalue attribute updategrams [SQLXML], null values nullvalue attribute null values [SQLXML]
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NULL Handling (SQLXML 4.0)

XML syntax denotes NULL as an absence. (For example, if an attribute or element value is NULL, that attribute or element is absent from the XML document.) In [!INCLUDEmsCoName] SQLXML, the updg:nullvalue attribute enables specifying NULL for an element or attribute value.

For example, the following updategram ensures that the Title value for a contact with ContactID of 64 is NULL, and then updates the Title value to "Mr." for this contact.

<ROOT xmlns:updg="urn:schemas-microsoft-com:xml-updategram">  
  <updg:sync updg:nullvalue="IsNULL"  >  
    <updg:before>  
       <Person.Contact ContactID="64" Title="IsNULL" />  
    </updg:before>  
    <updg:after>  
       <Person.Contact ContactID="64" Title="Mr." />  
    </updg:after>  
  </updg:sync>  
</ROOT>  

When parameters are passed to an updategram, NULL can be passed as the parameter value. This is done by specifying the nullvalue attribute in the <updg:header> block. For an example, see Passing Parameters to Updategrams (SQLXML 4.0).

See Also

Updategram Security Considerations (SQLXML 4.0)