通过

示例：指定 ELEMENTXSINIL 指令

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适用于：SQL Server Azure SQL 数据库 Azure SQL 托管实例

当指定 ELEMENT 指令检索以元素为中心的 XML 时，如果列具有 NULL 值，则 EXPLICIT 模式将不生成相应的元素。 另外，也可以指定 ELEMENTXSINIL 指令以请求为 xsi:nil 属性设置为 TRUE 值的 NULL 值生成元素。

以下查询构造包括雇员地址的 XML。 对于 AddressLine2 和 City 列，列名指定 ELEMENTXSINIL 指令。 这将为行集中的 AddressLine2 和 City 列中的 NULL 值生成元素。

USE AdventureWorks2022;
GO
SELECT 1    as Tag,
       NULL as Parent,
       E.BusinessEntityID  as [Employee!1!EmpID],
       BEA.AddressID as [Employee!1!AddressID],
       NULL        as [Address!2!AddressID],
       NULL        as [Address!2!AddressLine1!ELEMENT],
       NULL        as [Address!2!AddressLine2!ELEMENTXSINIL],
       NULL        as [Address!2!City!ELEMENTXSINIL]
FROM   HumanResources.Employee AS E
INNER JOIN Person.BusinessEntityAddress AS BEA
    ON E.BusinessEntityID = BEA.BusinessEntityID

UNION ALL
SELECT 2 as Tag,
       1 as Parent,
       E.BusinessEntityID,
       BEA.AddressID,
       A.AddressID,
       AddressLine1,
       AddressLine2,
       City
FROM   HumanResources.Employee AS E
INNER JOIN Person.BusinessEntityAddress AS BEA
    ON E.BusinessEntityID = BEA.BusinessEntityID
INNER JOIN Person.Address AS A
    ON BEA.AddressID = A.AddressID
ORDER BY [Employee!1!EmpID],[Address!2!AddressID]
FOR XML EXPLICIT;

下面是部分结果：

<Employee xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          EmpID="1"
          AddressID="249">
  <Address AddressID="249">
    <AddressLine1>4350 Minute Dr.</AddressLine1>
    <AddressLine2 xsi:nil="true" />
    <City>Minneapolis</City>
  </Address>
</Employee>
...

另请参阅