Question

我已经查看了许多在SQL Server中模拟“Group concat”功能的解决方案。我想制作一个更具人性化的解决方案，但我无法弄清楚如何做到这一点。

我有一个观点：

ParentID | ChildName

其中包含记录，例如：

1 | Max
1 | Jessie
2 | Steven
2 | Lucy
2 | Jake
3 | Mark

我希望“Group Concat”这些得到：

1 | Max and Jessie
2 | Steven, Lucy and Jake
3 | Mark

所以如果只有一个孩子，只需返回姓名，如果有多个孩子，则将最后两个用'和'连接，其他所有用'和'连接。

我不知道如何在不诉诸CLR的情况下做到这一点，我不想这样做。我很满意一个功能 - 但速度是一个问题，我如何确定孩子号码，以便我可以在'和'，'，'或''之间做出选择？

Answer 1

制作更易读的解决方案

抱歉，这是我能满足您要求的最佳方式。

SQL Fiddle

MS SQL Server 2008架构设置：

create table YourTable
(
  ParentID int,
  ChildName varchar(10)
);

insert into YourTable values
(1, 'Max'),
(1, 'Jessie'),
(2, 'Steven'),
(2, 'Lucy'),
(2, 'Jake'),
(3, 'Mark');

查询1 ：

with T as 
(
  select ParentID,
         ChildName,
         row_number() over(partition by ParentID order by ChildName) as rn,
         count(*) over(partition by ParentID) as cc
  from YourTable
)
select T1.ParentID,
       (
         select case
                  when T2.rn = 1 and T2.cc > 1 then ' and '
                  else ', ' 
                end + T2.ChildName
         from T as T2
         where T1.ParentID = T2.ParentID
         order by T2.rn desc
         for xml path(''), type
       ).value('substring(text()[1], 3)', 'varchar(max)') as ChildNames
from T as T1
group by T1.ParentID

<强> Results ：

| PARENTID |            CHILDNAMES |
------------------------------------
|        1 |        Max and Jessie |
|        2 | Steven, Lucy and Jake |
|        3 |                  Mark |

Answer 2

select ParentID,STUFF((SELECT ' and '+ChildName
    FROM Table1 where ParentID=a.ParentID
     FOR XML PATH('')),1,4,'')  as cnmae from Table1 a
group by ParentID

SQL FIDDLE DEMO

Answer 3

良好的逻辑问题。请检查下面的查询（有点冗长，但无法阻止我自己发布我的小逻辑:)）。

CREATE TABLE #SampleTable ([ParentID] int, [ChildName] varchar(6));

INSERT INTO #SampleTable VALUES (1, 'Max')
INSERT INTO #SampleTable VALUES (1, 'Jessie')
INSERT INTO #SampleTable VALUES (2, 'Steven')
INSERT INTO #SampleTable VALUES (2, 'Lucy')
INSERT INTO #SampleTable VALUES (2, 'Jake')
INSERT INTO #SampleTable VALUES (3, 'Mark')

select * From #SampleTable

;WITH T(xParentID, xChildName, xChildNameResult, xC1, xC2)AS
(
    SELECT * FROM(
    SELECT 
        ParentID ,
        ChildName, 
        CAST(ChildName AS NVARCHAR(MAX)) AS ChildNameResult,
        ROW_NUMBER() OVER (PARTITION BY [ParentID] ORDER BY ChildName) C1,
        COUNT(*) OVER (PARTITION BY [ParentID]) C2
    FROM #SampleTable)x WHERE x.C1=1

    UNION ALL

    SELECT ParentID, ChildName,
    CAST(T.xChildNameResult+(CASE WHEN C1=1 THEN '' WHEN C1=C2 THEN ' and ' ELSE ', ' END)+ChildName AS NVARCHAR(MAX)), C1, C2 
    FROM
    (
        SELECT 
        ParentID , 
            ChildName, 
            ROW_NUMBER() OVER (PARTITION BY ParentID order by ChildName) C1,
            COUNT(*) OVER (PARTITION BY ParentID) C2
        FROM #SampleTable
    )y INNER JOIN T ON y.ParentID=T.xParentID and y.c1=T.xC1+1
)SELECT xParentID, xChildNameResult FROM T where xC1=xC2
OPTION (MAXRECURSION 0);

SQL Server Group_concat具有不同的字符

3 个答案: