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Columns that contain a null value by default

  • Artikkeli

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance

By default, a null value in a column maps to the absence of the attribute, node, or element. This default behavior can be overridden by using the ELEMENTS XSINIL keyword phrase. This phrase requests element-centric XML. This means that null values are explicitly indicated in the returned results. These elements will have no value.

The ELEMENTS XSINIL phrase is shown in the following Transact-SQL SELECT example.

SELECT EmployeeID as "@EmpID",
       FirstName  as "EmpName/First",
       MiddleName as "EmpName/Middle",
       LastName   as "EmpName/Last"
FROM   HumanResources.Employee E, Person.Contact C
WHERE  E.EmployeeID = C.ContactID
  AND  E.EmployeeID=1
FOR XML PATH, ELEMENTS XSINIL;

The following shows the result. If XSINIL isn't specified, the <Middle> element will be absent.

<row xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" EmpID="1">
  <EmpName>
    <First>Gustavo</First>
    <Middle xsi:nil="true" />
    <Last>Achong</Last>
  </EmpName>
</row>

See also