Generating Elements for NULL Values Using the XSINIL Parameter
The ELEMENTS directive constructs XML in which each column value maps to an element in the XML. If the column value is NULL, no element is added. By specifying the optional XSINIL parameter on the ELEMENTS directive, you can request that an element also be created for the NULL value. In this case, an element that has the xsi:nil attribute set to TRUE is returned for each NULL column value.