create table t(C1 int, C2 nvarchar(2))
insert t select 1006, 'A'
insert t select 1006, 'B'
insert t select 1007, 'D'
insert t select 1007, 'C'
go
create function test_f(@C1 int)
returns nvarchar(200)
as
begin
declare @s nvarchar(200)
select @s=isnull(@s+',','')+C2 from t where C1=@C1
return @s
end
go
select distinct C1,[C2]=dbo.test_f(C1) from t
go
C1 C2
----------- --------------------
1006 A,B
1007 D,C(所影响的行数为 2 行)
insert t select 1006, 'A'
insert t select 1006, 'B'
insert t select 1007, 'D'
insert t select 1007, 'C'
go
create function test_f(@C1 int)
returns nvarchar(200)
as
begin
declare @s nvarchar(200)
select @s=isnull(@s+',','')+C2 from t where C1=@C1
return @s
end
go
select distinct C1,[C2]=dbo.test_f(C1) from t
go
C1 C2
----------- --------------------
1006 A,B
1007 D,C(所影响的行数为 2 行)
create function test_f(@C1 int)
returns nvarchar(20)
as
begin
declare @s nvarchar(20)
select @s=isnull(@s+',','')+C2 from t where C1=@C1 order by C2 --加一个排序
return @s
end
go
select distinct C1,[C2]=dbo.test_f(C1) from t
go
C1 C2
----------- --------------------
1006 A,B
1007 C,D(所影响的行数为 2 行)
go
create function test_f(@C1 int)
returns nvarchar(200)
as
begin
declare @s nvarchar(200)
set @s=''
select @s=@s+','++C2 from t where C1=@C1 order by C2 --加一个排序
return stuff(@s,1,1,'')
end
go
-----------
1006 A,B
1007 C,D(所影响的行数为 2 行)
--2、用游标循环。--写自定义函数比较简单。create table t(c1 varchar(100), c2 varchar(100)) insert t select 1006,'a'
insert t select 1006,'b'
insert t select 1007,'d'
insert t select 1007,'c' go
create function dbo.fn_Merge(@c1 varchar(100))
returns varchar(80)
as
begin
declare @s varchar(200)
set @s=''
select @s=@s+','+c2 from t where c1=@c1 order by c2
set @s=stuff(@s,1,1,'')
return @s
end
go
select c1,dbo.fn_Merge(c1) from t group by c1drop table t
drop function dbo.fn_merge
insert into tb values('1006','A')
insert into tb values('1006','B')
insert into tb values('1007','D')
insert into tb values('1007','C')
go--在SQL 2000中创建一个合并的函数
create function f_hb(@C1 int)
returns varchar(8000)
as
begin
declare @str varchar(8000)
set @str = ''
select @str = @str + ',' + cast(c2 as varchar) from tb where c1 = @C1
set @str = right(@str , len(@str) - 1)
return(@str)
End
go--调用自定义函数得到结果:
select distinct c1 ,dbo.f_hb(c1) as c2 from tb
drop table tb
drop function f_hb/*
c1 c2
---------- --------
1006 A,B
1007 D,C(所影响的行数为 2 行)
*/
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
insert into test(c1,c2) select '1006','a'
union all select '1006','b'
union all select '1007','c'
union all select'1007','d'
declare @c1 varchar(10)
set @c1=''
create table #t(c1 varchar(100) null,c2 varchar(100) null)
declare cur_t cursor for select distinct c1 from test
open cur_t
fetch cur_t into @c1
while @@fetch_status=0
begin
declare @c2 varchar(200)
select @c2=isnull(@c2,'')+','+c2 from test where c1=@c1
select @c2=substring(@c2,2,len(@c2))
insert into #t(c1,c2) select @c1,@c2
set @c2=null
fetch cur_t into @c1
end
select * from #t
drop table #t
close cur_t
deallocate cur_t
drop table test