SQL Sever中使用SQL语句实现把重复行数据合并为一行并用逗号分隔

一.定义表变量

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
-----最优的方式

SELECT CityName,STUFF((SELECT ',' + UserName FROM @T1 subTitle WHERE CityName=A.CityName FOR XML PATH('')),1, 1, '') AS A

FROM @T1 A

GROUP BY CityName
----第二种方式

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
stuff(select ',' + fieldname  from tablename for xml path('')),1,1,'')

这一整句的作用是将多行fieldname字段的内容串联起来，用逗号分隔。
for xml path是SQL Server 2005以后版本支持的一种生成XML的方式。
stuff函数的作用是去掉字符串最前面的逗号分隔符。

效果图：