在SQL Server 2005中

SELECT Stuff(
  (SELECT N', ' + Name FROM Names FOR XML PATH(''),TYPE)
  .value('text()[1]','nvarchar(max)'),1,2,N'')

在SQL Server 2016中

可以使用FOR JSON语法

即

SELECT per.ID,
Emails = JSON_VALUE(
   REPLACE(
     (SELECT _ = em.Email FROM Email em WHERE em.Person = per.ID FOR JSON PATH)
    ,'"},{"_":"',', '),'$[0]._'
) 
FROM Person per

结果会变成

Id  Emails
1   abc@gmail.com
2   NULL
3   def@gmail.com, xyz@gmail.com

即使您的数据包含无效的XML字符，这也会起作用

“”}，｛“_”：“”是安全的，因为如果您的数据包含“”｝，｛”_“：“”，它将被转义为“｝，{\”_\“：\”

可以用任何字符串分隔符替换“，”

在SQL Server 2017中，Azure SQL数据库

您可以使用新的STRING_AGG函数

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

我在家里无法访问SQL Server，所以我猜测这里的语法，但大致上是这样的：

DECLARE @names VARCHAR(500)

SELECT @names = @names + ' ' + Name
FROM Names

MySQL完整示例：

我们有很多用户可以拥有大量数据，我们希望有一个输出，我们可以在列表中看到所有用户的数据：

结果：

___________________________
| id   |  rowList         |
|-------------------------|
| 0    | 6, 9             |
| 1    | 1,2,3,4,5,7,8,1  |
|_________________________|

表格设置：

CREATE TABLE `Data` (
  `id` int(11) NOT NULL,
  `user_id` int(11) NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=latin1;


INSERT INTO `Data` (`id`, `user_id`) VALUES
(1, 1),
(2, 1),
(3, 1),
(4, 1),
(5, 1),
(6, 0),
(7, 1),
(8, 1),
(9, 0),
(10, 1);


CREATE TABLE `User` (
  `id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;


INSERT INTO `User` (`id`) VALUES
(0),
(1);

查询：

SELECT User.id, GROUP_CONCAT(Data.id ORDER BY Data.id) AS rowList FROM User LEFT JOIN Data ON User.id = Data.user_id GROUP BY User.id

提出了递归CTE解决方案，但没有提供代码。下面的代码是递归CTE的示例。

请注意，虽然结果与问题相符，但数据与给定的描述并不完全相符，因为我假设您确实希望对行组（而不是表中的所有行）执行此操作。将其更改为与表中的所有行相匹配是读者的练习。

;WITH basetable AS (
    SELECT
        id,
        CAST(name AS VARCHAR(MAX)) name,
        ROW_NUMBER() OVER (Partition BY id ORDER BY seq) rw,
        COUNT(*) OVER (Partition BY id) recs
    FROM (VALUES
        (1, 'Johnny', 1),
        (1, 'M', 2),
        (2, 'Bill', 1),
        (2, 'S.', 4),
        (2, 'Preston', 5),
        (2, 'Esq.', 6),
        (3, 'Ted', 1),
        (3, 'Theodore', 2),
        (3, 'Logan', 3),
        (4, 'Peter', 1),
        (4, 'Paul', 2),
        (4, 'Mary', 3)
    ) g (id, name, seq)
),
rCTE AS (
    SELECT recs, id, name, rw
    FROM basetable
    WHERE rw = 1

    UNION ALL

    SELECT b.recs, r.ID, r.name +', '+ b.name name, r.rw + 1
    FROM basetable b
    INNER JOIN rCTE r ON b.id = r.id AND b.rw = r.rw + 1
)
SELECT name
FROM rCTE
WHERE recs = rw AND ID=4
OPTION (MAXRECURSION 101)

以下是实现这一目标的完整解决方案：

-- Table Creation
CREATE TABLE Tbl
( CustomerCode    VARCHAR(50)
, CustomerName    VARCHAR(50)
, Type VARCHAR(50)
,Items    VARCHAR(50)
)

insert into Tbl
SELECT 'C0001','Thomas','BREAKFAST','Milk'
union SELECT 'C0001','Thomas','BREAKFAST','Bread'
union SELECT 'C0001','Thomas','BREAKFAST','Egg'
union SELECT 'C0001','Thomas','LUNCH','Rice'
union SELECT 'C0001','Thomas','LUNCH','Fish Curry'
union SELECT 'C0001','Thomas','LUNCH','Lessy'
union SELECT 'C0002','JOSEPH','BREAKFAST','Bread'
union SELECT 'C0002','JOSEPH','BREAKFAST','Jam'
union SELECT 'C0002','JOSEPH','BREAKFAST','Tea'
union SELECT 'C0002','JOSEPH','Supper','Tea'
union SELECT 'C0002','JOSEPH','Brunch','Roti'

-- function creation
GO
CREATE  FUNCTION [dbo].[fn_GetItemsByType]
(   
    @CustomerCode VARCHAR(50)
    ,@Type VARCHAR(50)
)
RETURNS @ItemType TABLE  ( Items VARCHAR(5000) )
AS
BEGIN

        INSERT INTO @ItemType(Items)
    SELECT  STUFF((SELECT distinct ',' + [Items]
         FROM Tbl 
         WHERE CustomerCode = @CustomerCode
            AND Type=@Type
            FOR XML PATH(''))
        ,1,1,'') as  Items



    RETURN 
END

GO

-- fianl Query
DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(Type) 
                    from Tbl
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT CustomerCode,CustomerName,' + @cols + '
             from 
             (
                select  
                    distinct CustomerCode
                    ,CustomerName
                    ,Type
                    ,F.Items
                    FROM Tbl T
                    CROSS APPLY [fn_GetItemsByType] (T.CustomerCode,T.Type) F
            ) x
            pivot 
            (
                max(Items)
                for Type in (' + @cols + ')
            ) p '

execute(@query)