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 元素，每一列的值作为 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: ----将元素命名为自定义的名称Employee |
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？
Nancy Davolio 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, LastNameFROM EmployeesORDER 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***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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