sql里将重复行数据合并为一行,将多行fieldname字段的内容串联起来，用逗号分隔，接下来为大家介绍下详细的实现sql语句，希望对你有所帮助
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：
