如何在sql中连接多个具有相同id的行？

Question

我的表包含两个字段的详细信息:

ID      DisplayName
1        Editor
1        Reviewer
7        EIC
7        Editor
7        Reviewer
7        Editor
19       EIC
19       Editor
19       Reviewer

我想用DisplayName获取独特的细节

1 Editor,Reviewer 7 EIC,Editor,Reviewer

不要使用ID 7获取重复值

如何组合DisplayName详细信息？如何编写查询？

Answer 1

在SQL-Server中,您可以执行以下操作:

QUERY

SELECT id, displayname = 
    STUFF((SELECT DISTINCT ', ' + displayname
           FROM #t b 
           WHERE b.id = a.id 
          FOR XML PATH('')), 1, 2, '')
FROM #t a
GROUP BY id

测试数据

create table #t 
(
id int,
displayname nvarchar(max)
)

insert into #t values    
 (1 ,'Editor')
,(1 ,'Reviewer')
,(7 ,'EIC')
,(7 ,'Editor')
,(7 ,'Reviewer')
,(7 ,'Editor')
,(19,'EIC')
,(19,'Editor')
,(19,'Reviewer')

OUTPUT

id  displayname
1   Editor, Reviewer
7   Editor, EIC, Reviewer
19  Editor, EIC, Reviewer

Answer 2

DECLARE @t TABLE
(
    ID INT,
    DisplayName VARCHAR(50)
)
INSERT INTO @t (ID, DisplayName)
VALUES
    (1 , 'Editor'),
    (1 , 'Reviewer'),
    (7 , 'EIC'),
    (7 , 'Editor'),
    (7 , 'Reviewer'),
    (7 , 'Editor'),
    (19, 'EIC'),
    (19, 'Editor'),
    (19, 'Reviewer')

SELECT *, STUFF((
            SELECT DISTINCT ', ' + DisplayName
            FROM @t
            WHERE ID = t.ID
            FOR XML PATH('')), 1, 2, '')
FROM (
    SELECT DISTINCT ID
    FROM @t
) t

输出 -

----------- ------------------------
1           Editor, Reviewer
7           Editor, EIC, Reviewer
19          Editor, EIC, Reviewer

关于字符串聚合的帖子:

http://www.codeproject.com/Articles/691102/String-Aggregation-in-the-World-of-SQL-Server

Answer 3

对于 MySQL：
SELECT id, GROUP_CONCAT(displayname) FROM tableName GROUP BY id

参考：http : //www.sqlines.com/mysql/functions/group_concat

Answer 4

SQL Server 2017+ 和 SQL Azure：STRING_AGG

从 SQL Server 的下一个版本开始，我们最终可以跨行连接，而不必求助于任何变量或 XML 巫术。

STRING_AGG (Transact-SQL)

SELECT ID, STRING_AGG(DisplayName, ', ') AS DisplayNames
FROM TableName
GROUP BY ID