SQL 合并多行记录的方法总汇

sql中合并多行记录的方法总汇:

--1. 创建表，添加测试数据

CREATE TABLE tb(id int,[value] varchar(10))
INSERT tb SELECT 1,'aa'
UNION ALL SELECT 1,'bb'
UNION ALL SELECT 2,'aaa'
UNION ALL SELECT 2,'bbb'
UNION ALL SELECT 2,'ccc'
--SELECT * FROM tb
/*//
id value
----------- ----------
1 aa
1 bb
2 aaa
2 bbb
2 ccc
(5 row(s) affected)
/

--2 在sql2000只能用自定义函数实现

----2.1 创建合并函数fn_strSum，根据id合并value值
GO
CREATE FUNCTION dbo.fn_strSum(@id int)
RETURNS varchar(8000)
AS
BEGIN
DECLARE @values varchar(8000)
SET @values = ''
SELECT @values = @values + ',' + value FROM tb WHERE id=@id
RETURN STUFF(@values,1,'')
END
GO
-- 调用函数
SELECT id,VALUE = dbo.fn_strSum(id) FROM tb GROUP BY id
DROP FUNCTION dbo.fn_strSum
----2.2 创建合并函数fn_strSum2，根据id合并value值
GO
CREATE FUNCTION dbo.fn_strSum2(@id int)
RETURNS varchar(8000)
AS
BEGIN
DECLARE @values varchar(8000)
SELECT @values = isnull(@values + ',','') + value FROM tb WHERE id=@id
RETURN @values
END
GO
-- 调用函数
SELECT id,VALUE = dbo.fn_strSum2(id) FROM tb GROUP BY id
DROP FUNCTION dbo.fn_strSum2
--3 在sql2005/sql2008中的新解法
----3.1 使用OUTER APPLY
SELECT
FROM (SELECT disTINCT id FROM tb) A OUTER APPLY(
SELECT [values]= STUFF(REPLACE(REPLACE(
(
SELECT value FROM tb N
WHERE id = A.id
FOR XML AUTO
),'<N value="','),'"/>',''),'')
)N
----3.2 使用XML
SELECT id,[values]=STUFF((SELECT ','+[value] FROM tb t WHERE id=tb.id FOR XML PATH('')),'')
FROM tb
GROUP BY id
--4 删除测试表tb
drop table tb
/*//
id values
----------- --------------------
1 aa,bb
2 aaa,bbb,ccc
(2 row(s) affected)
*/

原文地址：https://www.jb51.cc/mssql/64369.html