SQL Sever中使用SQL語句實現(xiàn)把重復(fù)行數(shù)據(jù)合并為一行并用逗號分隔

    一.定義表變量
    代碼如下:
    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
    -----最優(yōu)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
    ----第二種方式
    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,'')
    這一整句的作用是將多行fieldname字段的內(nèi)容串聯(lián)起來，用逗號分隔。
    for xml path是SQL Server 2005以后版本支持的一種生成XML的方式。
    stuff函數(shù)的作用是去掉字符串最前面的逗號分隔符。