在MySQL中，有一个函数GROUP_CONCATT（），它允许您连接多行的值。例子：

SELECT 1 AS a, GROUP_CONCAT(name ORDER BY name ASC SEPARATOR ', ') AS people 
FROM users 
WHERE id IN (1,2,3) 
GROUP BY a

如果要处理null，可以通过添加where子句或在第一个子句周围添加另一个COALENCE来完成。

DECLARE @Names VARCHAR(8000) 
SELECT @Names = COALESCE(COALESCE(@Names + ', ', '') + Name, @Names) FROM People

SQL Server 2005或更高版本

CREATE TABLE dbo.Students
(
    StudentId INT
    , Name VARCHAR(50)
    , CONSTRAINT PK_Students PRIMARY KEY (StudentId)
);

CREATE TABLE dbo.Subjects
(
    SubjectId INT
    , Name VARCHAR(50)
    , CONSTRAINT PK_Subjects PRIMARY KEY (SubjectId)
);

CREATE TABLE dbo.Schedules
(
    StudentId INT
    , SubjectId INT
    , CONSTRAINT PK__Schedule PRIMARY KEY (StudentId, SubjectId)
    , CONSTRAINT FK_Schedule_Students FOREIGN KEY (StudentId) REFERENCES dbo.Students (StudentId)
    , CONSTRAINT FK_Schedule_Subjects FOREIGN KEY (SubjectId) REFERENCES dbo.Subjects (SubjectId)
);

INSERT dbo.Students (StudentId, Name) VALUES
    (1, 'Mary')
    , (2, 'John')
    , (3, 'Sam')
    , (4, 'Alaina')
    , (5, 'Edward')
;

INSERT dbo.Subjects (SubjectId, Name) VALUES
    (1, 'Physics')
    , (2, 'Geography')
    , (3, 'French')
    , (4, 'Gymnastics')
;

INSERT dbo.Schedules (StudentId, SubjectId) VALUES
    (1, 1)        --Mary, Physics
    , (2, 1)    --John, Physics
    , (3, 1)    --Sam, Physics
    , (4, 2)    --Alaina, Geography
    , (5, 2)    --Edward, Geography
;

SELECT
    sub.SubjectId
    , sub.Name AS [SubjectName]
    , ISNULL( x.Students, '') AS Students
FROM
    dbo.Subjects sub
    OUTER APPLY
    (
        SELECT
            CASE ROW_NUMBER() OVER (ORDER BY stu.Name) WHEN 1 THEN '' ELSE ', ' END
            + stu.Name
        FROM
            dbo.Students stu
            INNER JOIN dbo.Schedules sch
                ON stu.StudentId = sch.StudentId
        WHERE
            sch.SubjectId = sub.SubjectId
        ORDER BY
            stu.Name
        FOR XML PATH('')
    ) x (Students)
;

Oracle有两种方法：

    create table name
    (first_name varchar2(30));

    insert into name values ('Peter');
    insert into name values ('Paul');
    insert into name values ('Mary');

解决方案是1：

    select substr(max(sys_connect_by_path (first_name, ',')),2) from (select rownum r, first_name from name ) n start with r=1 connect by prior r+1=r
    o/p=> Peter,Paul,Mary

解决方案是2:

    select  rtrim(xmlagg (xmlelement (e, first_name || ',')).extract ('//text()'), ',') first_name from name
    o/p=> Peter,Paul,Mary

下面是一个使用“基本循环”和“rownum”实现给定场景的简单PL/SQL过程

表定义

CREATE TABLE "NAMES" ("NAME" VARCHAR2(10 BYTE))) ;

让我们将值插入此表

INSERT INTO NAMES VALUES('PETER');
INSERT INTO NAMES VALUES('PAUL');
INSERT INTO NAMES VALUES('MARY');

程序从这里开始

DECLARE 

MAXNUM INTEGER;
CNTR INTEGER := 1;
C_NAME NAMES.NAME%TYPE;
NSTR VARCHAR2(50);

BEGIN

SELECT MAX(ROWNUM) INTO MAXNUM FROM NAMES;

LOOP

SELECT NAME INTO  C_NAME FROM 
(SELECT ROWNUM RW, NAME FROM NAMES ) P WHERE P.RW = CNTR;

NSTR := NSTR ||','||C_NAME;
CNTR := CNTR + 1;
EXIT WHEN CNTR > MAXNUM;

END LOOP;

dbms_output.put_line(SUBSTR(NSTR,2));

END;

后果

PETER,PAUL,MARY

SQL Server中尚未通过XML data（）命令显示的一个方法是：

假设一个名为NameList的表有一列名为FName，

SELECT FName + ', ' AS 'data()'
FROM NameList
FOR XML PATH('')

返回：

"Peter, Paul, Mary, "

只需处理额外的逗号。

正如@NReilingh的注释所采用的，您可以使用以下方法删除尾随逗号。假设表和列名相同：

STUFF(REPLACE((SELECT '#!' + LTRIM(RTRIM(FName)) AS 'data()' FROM NameList
FOR XML PATH('')),' #!',', '), 1, 2, '') as Brands