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create function f_joinSTR
(@id int)
returns varchar(8000)
as
begin
declare @str varchar(8000)
set @str=''
select @str=@str + ',' + name from tb where a_id=@id
set @str=stuff(@str,1,1,'')
return @str
end
select *,dbo.f_joinSTR(id) name from ta
CREATE TABLE 表A
(
id int,
title varchar(20),
content varchar(20)
)
CREATE TABLE 表B
(
a_id int,
name varchar(20)
)
insert into 表A
SELECT 1,'a','aa' union all
SELECT 2,'b','bb' union all
SELECT 3,'c','cc'
insert into 表B
SELECT 1,'张三' union all
SELECT 1,'李四' union all
SELECT 2,'王二' union all
SELECT 3,'王一' union all
SELECT 3,'赵六' union all
SELECT 3,'钱二'
GO
CREATE FUNCTION F_UNION(@id int)
RETURNS VARCHAR(50)
AS
BEGIN
DECLARE @re VARCHAR(50)
SET @re = ''
SELECT @re = @re + ','+ name
FROM 表B
WHERE a_id = @id
GROUP BY a_id,name
RETURN (STUFF(@re,1,1,''))
END
GO
SELECT *,name=DBO.F_UNION(id) FROM 表A
DROP FUNCTION F_UNION
DROP TABLE 表A,表B
id title content name
----------- -------------------- -------------------- --------------------------------------------------
1 a aa 李四,张三
2 b bb 王二
3 c cc 钱二,王一,赵六
(所影响的行数为 3 行)
create table uu(id int,title varchar(10),content varchar(20))
insert uu select 1,'a','aa'
union all select 2,'b','bb'
union all select 3,'c','cc'
go
create table uuu(a_id int,name varchar(20))
insert uuu select 1,'张三'
union all select 1,'李四'
union all select 2,'王二'
union all select 3,'王一'
union all select 3,'赵六'
union all select 3,'钱二'
go
create function GetVa(@id int)
returns varchar(1000)
as
begin
declare @sql varchar(1000)
select @sql=isnull(@sql+',','')+name from uuu where a_id=@id
return @sql
end
go
select uu.*,name from uu inner join (select a_id,dbo.getVa(a_id) name from uuu group by a_id)uuu
on uu.id=uuu.a_id
--result
/*id title content ame
----------- ---------- ------------- --------------------------
1 a aa 张三,李四
2 b bb 王二
3 c cc 王一,赵六,钱二
(所影响的行数为 3 行)
*/
--下面有2005的写法:
问题描述:
无论是在sql 2000, 还是在 sql 2005 中,都没有提供字符串的聚合函数,
所以, 当我们在处理下列要求时,会比较麻烦:
有表tb, 如下:
id value
----- ------
1 aa
1 bb
2 aaa
2 bbb
2 ccc
需要得到结果:
id values
------ -----------
1 aa,bb
2 aaa,bbb,ccc
即, group by id, 求 value 的和(字符串相加)
1. 旧的解决方法
-- 1. 创建处理函数
CREATE FUNCTION dbo.f_str(@id int)
RETURNS varchar(8000)
AS
BEGIN
DECLARE @r varchar(8000)
SET @r = ''
SELECT @r = @r + ',' + value
FROM tb
WHERE id=@id
RETURN STUFF(@r, 1, 1, '')
END
GO
-- 调用函数
SELECt id, values=dbo.f_str(id)
FROM tb
GROUP BY id
-- 2. 新的解决方法
-- 示例数据
DECLARE @t TABLE(id int, value varchar(10))
INSERT @t SELECT 1, 'aa'
UNION ALL SELECT 1, 'bb'
UNION ALL SELECT 2, 'aaa'
UNION ALL SELECT 2, 'bbb'
UNION ALL SELECT 2, 'ccc'
-- 查询处理
SELECT *
FROM(
SELECT DISTINCT
id
FROM @t
)A
OUTER APPLY(
SELECT
[values]= STUFF(REPLACE(REPLACE(
(
SELECT value FROM @t N
WHERE id = A.id
FOR XML AUTO
), '<N value="', ','), '"/>', ''), 1, 1, '')
)N
/*--结果
id values
----------- ----------------
1 aa,bb
2 aaa,bbb,ccc
(2 行受影响)
--*/
附: 合并与分拆的CLR, sql2005的示例中有:
在安装sql 2005的示例后,默认安装目录为 drive:\Program Files\Microsoft SQL Server\90\Samples\Engine\Programmability\CLR\StringUtilities中
create table A(id int,title varchar(10),content varchar(10))
insert into A values(1, 'a', 'aa')
insert into A values(2, 'b', 'bb')
insert into A values(3, 'c', 'cc')
create table B(a_id int,name varchar(10))
insert into B values(1, '张三')
insert into B values(1, '李四')
insert into B values(2, '王二')
insert into B values(3, '王一')
insert into B values(3, '赵六')
insert into B values(3, '钱二')
go
--创建一个合并的函数
create function f_hb(@a_id int)
returns varchar(8000)
as
begin
declare @str varchar(8000)
set @str = ''
select @str = @str + ',' + cast(name as varchar) from B where a_id = @a_id
set @str = right(@str , len(@str) - 1)
return(@str)
End
go
--调用自定义函数得到结果:
select A.* , T.name from A,
(select distinct a_id ,dbo.f_hb(a_id) as name from B) T
where A.id = T.a_id
drop table A,B
drop function f_hb
/*
id title content name
----------- ---------- ---------- ---------------
1 a aa 张三,李四
2 b bb 王二
3 c cc 王一,赵六,钱二
(所影响的行数为 3 行)
*/