null-handling-sqlxml-4-0.md

title	NULL Handling (SQLXML)
description	Learn how NULL attributes or elements can be specified in an SQLXML 4.0 updategram by using the updg:nullvalue attribute.
author	MikeRayMSFT
ms.author	mikeray
ms.date	03/17/2017
ms.service	sql
ms.subservice	xml
ms.topic	reference
monikerRange	=azuresqldb-current||>=sql-server-2016||>=sql-server-linux-2017||=azuresqldb-mi-current

NULL Handling (SQLXML 4.0)

[!INCLUDE SQL Server Azure SQL Database] 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)