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
使用COALESCE-从这里了解更多信息
例如:
102103104
然后在SQL Server中编写以下代码,
Declare @Numbers AS Nvarchar(MAX) -- It must not be MAX if you have few numbers
SELECT @Numbers = COALESCE(@Numbers + ',', '') + Number
FROM TableName where Number IS NOT NULL
SELECT @Numbers
输出将是:
102,103,104
其他回答
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)
;
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
在SQL Server 2017或更高版本中,可以使用STRING_AGG()函数生成逗号分隔的值。请看下面的一个示例。
SELECT
VendorId, STRING_AGG(FirstName,',') UsersName
FROM Users
WHERE VendorId != 9
GROUP BY VendorId
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
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