sql里将重复行数据合并为一行数据使用逗号进行分隔

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我是靠谱客的博主明理店员，最近开发中收集的这篇文章主要介绍sql里将重复行数据合并为一行数据使用逗号进行分隔，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

一.定义表变量

复制代码代码如下:

 
DECLARE @T1 table 
( 
UserID int , 
UserName nvarchar(50), 
CityName nvarchar(50) 
); 

复制代码代码如下:

 
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') 

复制代码代码如下:

 
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,'') 