SQL Server2005 使用FOR XML选项进行字符串的串联聚合

使用FOR XML查询选项的PATH模式，可以用于字符串的串联聚合，并且可以很方便地组织聚合后的文本描述。

先看看下面的节选：

with arg1 as

(

select top 10 [lt_username],(

select CAST(n2.room as nvarchar(128) )+':'+CAST(n2.point as nvarchar(8))+',' as [text()]

from [newbbspoints] n2

where n2.lt_username = n1.lt_username

order by n2.point desc

for xml path('')

) as [Description]

from dbo.[newbbspoints] as n1

)

select [lt_username], stuff([Description], Len([Description]), 1, '') as [Description] from arg1

使用for xml path('')提供了一个空字符串作为输入，所以未产生包装器(wrapper)元素，

通过CAST(n2.room as nvarchar(128) )+':'+CAST(n2.point as nvarchar(8))+','

可以利用各列的数据来串联出此字段的描述。

其中使用stuff截取最后一个生成的分割符','

以下的例子利用一个已在存在表的数据去更新另外一下表，更新的字段内容为第一个表的两个字段的字符串串联。

if object_id('dbo.BBSPoints') is not null

drop table dbo.BBSPoints

if object_id('dbo.CJB_Temp') is not null

drop table dbo.CJB_Temp;

create table dbo.BBSPoints

(

lt_username nvarchar(20) not null,

room nvarchar(128) not null,

point int

)

insert into dbo.BBSPoints(lt_username,room,point) values(N'zdg',N'社区支持',2734);

insert into dbo.BBSPoints(lt_username,room,point) values(N'zdg',N'扩充话题',2734);

insert into dbo.BBSPoints(lt_username,room,point) values(N'billok',N'产品/厂家',654);

insert into dbo.BBSPoints(lt_username,room,point) values(N'billok',N'MS-SQL Server',45);

insert into dbo.BBSPoints(lt_username,room,point) values(N'junbiaochen',N'C#',785);

insert into dbo.BBSPoints(lt_username,room,point) values(N'junbiaochen',N'asp.net',265);

create table dbo.CJB_Temp

(

UserName nvarchar(20) not null primary key,

Title nvarchar(256)

)

insert into dbo.CJB_Temp(UserName,Title) values(N'zdg',N'');

insert into dbo.CJB_Temp(UserName,Title) values(N'billok',N'');

insert into dbo.CJB_Temp(UserName,Title) values(N'junbiaochen',N'');

with arg1 as

(

select [lt_username],(

select CAST(n2.room as nvarchar(128) )+':'+CAST(n2.point as nvarchar(8))+',' as [text()]

from dbo.[BBSPoints] n2

where n2.lt_username = n1.lt_username

order by n2.point desc

for xml path('')

) as [Description]

from dbo.[BBSPoints] as n1

)

,arg2 as

(

select [lt_username], stuff([Description], len([Description]), 1, '') as [Description] from arg1

)

update t

set [Title] = a2.[Description]

from dbo.[CJB_Temp] t

join arg2 a2 on a2.[lt_username] = t.[UserName]

select * from dbo.[CJB_Temp];

drop table dbo.[BBSPoints];

drop table dbo.[CJB_Temp];