【T-SQL系列】FOR XML PATH 语句的应用

DECLARE @TempTable TABLE
(
UserID INT ,
UserName NVARCHAR(50)
);
INSERT  INTO @TempTable
( UserID, UserName )
VALUES  ( 1, 'a' )
INSERT  INTO @TempTable
( UserID, UserName )
VALUES  ( 2, 'b' )

SELECT  UserID ,
UserName
FROM    @TempTable
FOR     XML PATH

--其实PATH() 括号内的参数是控制节点名称的
SELECT  UserID ,
UserName
FROM    @TempTable
FOR     XML PATH('lzy')

--这样就不显示上级节点了
SELECT  UserID ,
UserName
FROM    @TempTable
FOR     XML PATH('')

--大家可以根据自己需要的格式进行组合
SELECT  CAST(UserID AS VARCHAR) + '' ,
UserName + ''
FROM    @TempTable
FOR     XML PATH('')

SELECT  CAST(UserID AS VARCHAR) + ',' ,
UserName + '' ,
';'
FROM    @TempTable
FOR     XML PATH('')

SELECT  '{' + CAST(UserID AS VARCHAR) + ',' ,
'"' + UserName + '"' ,
'}'
FROM    @TempTable
FOR     XML PATH('')

DECLARE @T1 TABLE
(
UserID INT ,
UserName NVARCHAR(50) ,
CityName NVARCHAR(50)
);
INSERT  INTO @T1
( UserID, UserName, CityName )
VALUES  ( 1, 'a', '上海' )
INSERT  INTO @T1
( UserID, UserName, CityName )
VALUES  ( 2, 'b', '北京' )
INSERT  INTO @T1
( UserID, UserName, CityName )
VALUES  ( 3, 'c', '上海' )
INSERT  INTO @T1
( UserID, UserName, CityName )
VALUES  ( 4, 'd', '北京' )
INSERT  INTO @T1
( UserID, UserName, CityName )
VALUES  ( 5, 'e', '上海' )

SELECT  *
FROM    @T1

SELECT  CityName ,
( SELECT    UserName + ','
FROM      @T1
WHERE     CityName = A.CityName
FOR
XML PATH('')
) AS UserList
FROM    @T1 A
GROUP BY CityName

--生成结果（每个城市的用户名）

SELECT  B.CityName ,
LEFT(UserList, LEN(UserList) - 1)
FROM    ( SELECT    CityName ,
( SELECT    UserName + ','
FROM      @T1
WHERE     CityName = A.CityName
FOR
XML PATH('')
) AS UserList
FROM      @T1 A
GROUP BY  CityName
) B