FOR XML子句有四种最基本的模式，如上图所示：
1、AUTO模式：返回数据表为起表名的元素，每一列的值返回为属性；
2、RAW模式：返回数据行为<Row>元素，每一列的值作为<Row>元素的属性；
3、PATH模式：通过简单的XPath语法来允许用户自定义嵌套的XML结构、元素、属性值
4、EXPLICIT模式：通过SELECT语法定义输出XML的结构
具体实例如下：
1、AUTO模式
(1). SQL语句：
1: SELECT EmployeeID,FirstName,LastName FROM Employees FOR XML AUTO, XMLSCHEMA
(2). 所生成的XML文件：
返回XML文件的XML Schema
<xsd:schema targetNamespace="urn:schemas-microsoft-com:sql:SqlRowSet1" xmlns:schema="urn:schemas-microsoft-com:sql:SqlRowSet1" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:sqltypes="http://schemas.microsoft.com/sqlserver/2004/sqltypes" elementFormDefault="qualified">
<xsd:import namespace="http://schemas.microsoft.com/sqlserver/2004/sqltypes" schemaLocation="http://schemas.microsoft.com/sqlserver/2004/sqltypes/sqltypes.xsd" />
<xsd:element name="Employees">
<xsd:complexType>
<xsd:attribute name="EmployeeID" type="sqltypes:int" use="required" />
<xsd:attribute name="FirstName" use="required">
<xsd:simpleType>
<xsd:restriction base="sqltypes:nvarchar" sqltypes:localeId="1033" sqltypes:sqlCompareOptions="IgnoreCase IgnoreKanaType IgnoreWidth" sqltypes:sqlSortId="52">
<xsd:maxLength value="10" />
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
<xsd:attribute name="LastName" use="required">
<xsd:simpleType>
<xsd:restriction base="sqltypes:nvarchar" sqltypes:localeId="1033" sqltypes:sqlCompareOptions="IgnoreCase IgnoreKanaType IgnoreWidth" sqltypes:sqlSortId="52">
<xsd:maxLength value="20" />
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
</xsd:complexType>
</xsd:element>
</xsd:schema>
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="1" FirstName="Nancy" LastName="Davolio" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="2" FirstName="Andrew" LastName="Fuller" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="3" FirstName="Janet" LastName="Leverling" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="4" FirstName="Margaret" LastName="Peacock" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="5" FirstName="Steven" LastName="Buchanan" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="6" FirstName="Michael" LastName="Suyama" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="7" FirstName="Robert" LastName="King" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="8" FirstName="Laura" LastName="Callahan" />
<Employees xmlns="urn:schemas-microsoft-com:sql:SqlRowSet1" EmployeeID="9" FirstName="Anne" LastName="Dodsworth" />
2、RAW模式
(1). SQL语句：
1: ----将元素命名为自定义的名称Employee
2: SELECT EmployeeID,FirstName,LastName FROM Employees FOR XML RAW ('Employee')
(2). 所生成的XML文件：
1: <Employee EmployeeID="1" FirstName="Nancy" LastName="Davolio" />
2: <Employee EmployeeID="2" FirstName="Andrew" LastName="Fuller" />
3: <Employee EmployeeID="3" FirstName="Janet" LastName="Leverling" />
4: <Employee EmployeeID="4" FirstName="Margaret" LastName="Peacock" />
5: <Employee EmployeeID="5" FirstName="Steven" LastName="Buchanan" />
6: <Employee EmployeeID="6" FirstName="Michael" LastName="Suyama" />
7: <Employee EmployeeID="7" FirstName="Robert" LastName="King" />
8: <Employee EmployeeID="8" FirstName="Laura" LastName="Callahan" />
9: <Employee EmployeeID="9" FirstName="Anne" LastName="Dodsworth" />
3、PATH模式：
(1). SQL语句：
SELECT EmployeeID "@ID",FirstName "Name/FirstName",LastName "Name/LastName"
FROM Employees FOR XML PATH ('Employee')
(2). 所生成的XML文件
<Employee ID="1">
<Name>
<FirstName>Nancy</FirstName>
<LastName>Davolio</LastName>
</Name>
</Employee>
<Employee ID="2">
<Name>
<FirstName>Andrew</FirstName>
<LastName>Fuller</LastName>
</Name>
</Employee>
<Employee ID="3">
<Name>
<FirstName>Janet</FirstName>
<LastName>Leverling</LastName>
</Name>
</Employee>
<Employee ID="4">
<Name>
<FirstName>Margaret</FirstName>
<LastName>Peacock</LastName>
</Name>
</Employee>
<Employee ID="5">
<Name>
<FirstName>Steven</FirstName>
<LastName>Buchanan</LastName>
</Name>
</Employee>
<Employee ID="6">
<Name>
<FirstName>Michael</FirstName>
<LastName>Suyama</LastName>
</Name>
</Employee>
<Employee ID="7">
<Name>
<FirstName>Robert</FirstName>
<LastName>King</LastName>
</Name>
</Employee>
<Employee ID="8">
<Name>
<FirstName>Laura</FirstName>
<LastName>Callahan</LastName>
</Name>
</Employee>
4、EXPLICIT模式
问题：加入要生成如下的XML文档该如何操作？
<Employee EmpID="1">
<FirstName>Nancy</FirstName>
<LastName>Davolio</LastName>
</Employee>
EXPLICIT模式解决这个问题的应用分为两个主要步骤：
1.定义要输出的XML文档结构；
2.传入实际的数据值；
(1). SQL语句：
--定义输出XML文档的数据结构
SELECT 1 AS Tag,
NULL AS Parent,
EmployeeID AS [Employee!1!EmpID],
FirstName AS [Employee!1!FirstName!element],
LastName AS [Employee!1!LastName!element]
FROM Employees
UNION ALL
--传入实际的数据
SELECT 1,
NULL,
EmployeeID,
FirstName,
LastName
FROM Employees
ORDER BY [Employee!1!EmpID],
[Employee!1!FirstName!element],
[Employee!1!LastName!element]
FOR XML EXPLICIT
语句含义的解释：
先看看定义XML结构的语句输出结果：
Tag栏用来指定生成元素的嵌套水平；1表示嵌套水平为
Parent栏用来指定当前Tag的父级层次；Null值表示该元素为顶级元素；
EmployeeID AS [Employee!1!EmpID],
说明：当前元素或属性的父级元素的名称！元素的标签号！元素或属性的名称
FirstName AS [Employee!1!FirstName!element],
说明：当前元素或属性的父级元素的名称！元素的标签号！元素或属性的名称！指定值作为元素输出
5、为输出的XML文档添加根元素(Root element)
(1). SQL语句：
SELECT EmployeeID,FirstName,LastName FROM Employees FOR XML AUTO, ROOT('MyRoot')
(2). 所生成的XML文件
<MyRoot>
<Employees EmployeeID="1" FirstName="Nancy" LastName="Davolio" />
<Employees EmployeeID="2" FirstName="Andrew" LastName="Fuller" />
<Employees EmployeeID="3" FirstName="Janet" LastName="Leverling" />
<Employees EmployeeID="4" FirstName="Margaret" LastName="Peacock" />
<Employees EmployeeID="5" FirstName="Steven" LastName="Buchanan" />
<Employees EmployeeID="6" FirstName="Michael" LastName="Suyama" />
<Employees EmployeeID="7" FirstName="Robert" LastName="King" />
<Employees EmployeeID="8" FirstName="Laura" LastName="Callahan" />
<Employees EmployeeID="9" FirstName="Anne" LastName="Dodsworth" />
</MyRoot>
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