考虑一个包含名称的数据库表,其中有三行:
Peter
Paul
Mary
有没有一种简单的方法可以把它变成彼得、保罗、玛丽的一串?
考虑一个包含名称的数据库表,其中有三行:
Peter
Paul
Mary
有没有一种简单的方法可以把它变成彼得、保罗、玛丽的一串?
当前回答
对于其他答案,阅读答案的人必须知道特定的域表,例如车辆或学生。必须创建该表并用数据填充该表以测试解决方案。
下面是一个使用SQL Server“Information_Schema.Columns”表的示例。通过使用此解决方案,不需要创建表或添加数据。此示例为数据库中的所有表创建一个逗号分隔的列名列表。
SELECT
Table_Name
,STUFF((
SELECT ',' + Column_Name
FROM INFORMATION_SCHEMA.Columns Columns
WHERE Tables.Table_Name = Columns.Table_Name
ORDER BY Column_Name
FOR XML PATH ('')), 1, 1, ''
)Columns
FROM INFORMATION_SCHEMA.Columns Tables
GROUP BY TABLE_NAME
其他回答
虽然为时已晚,而且已经有了许多解决方案。下面是MySQL的简单解决方案:
SELECT t1.id,
GROUP_CONCAT(t1.id) ids
FROM table t1 JOIN table t2 ON (t1.id = t2.id)
GROUP BY t1.id
使用递归查询,您可以执行以下操作:
-- Create example table
CREATE TABLE tmptable (NAME VARCHAR(30)) ;
-- Insert example data
INSERT INTO tmptable VALUES('PETER');
INSERT INTO tmptable VALUES('PAUL');
INSERT INTO tmptable VALUES('MARY');
-- Recurse query
with tblwithrank as (
select * , row_number() over(order by name) rang , count(*) over() NbRow
from tmptable
),
tmpRecursive as (
select *, cast(name as varchar(2000)) as AllName from tblwithrank where rang=1
union all
select f0.*, cast(f0.name + ',' + f1.AllName as varchar(2000)) as AllName
from tblwithrank f0 inner join tmpRecursive f1 on f0.rang=f1.rang +1
)
select AllName from tmpRecursive
where rang=NbRow
我真的很喜欢Dana回答的优雅,只想让它变得完整。
DECLARE @names VARCHAR(MAX)
SET @names = ''
SELECT @names = @names + ', ' + Name FROM Names
-- Deleting last two symbols (', ')
SET @sSql = LEFT(@sSql, LEN(@sSql) - 1)
在SQL Server中实现这一点的一种方法是将表内容返回为XML(对于XML原始),将结果转换为字符串,然后用“,”替换标记。
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)
;