一、问题
select UserID,LastName,FirstName,UserName
From SYSUser
UserID LastName FirstName UserName
------------------------------------------------------
1
A
B
C
2
A1
B1
C1
3
A2
B2
C2
|
我想把这个select出来的纪录集拼接成一个字符串。应该怎么实现?例如:
二、解决
SQL code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)
方法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
|
方法2、新的解决方法
1、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' |
2、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 |
3、结果
id
values
----------- ----------------
1
aa,bb
2
aaa,bbb,ccc
(2 行受影响) |
三、各种字符串分函数
--3.3.1 使用游标法进行字符串合并处理的示例。
--处理的数据
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',1
UNION ALL SELECT 'a',2
UNION ALL SELECT 'b',1
UNION ALL SELECT 'b',2
UNION ALL SELECT 'b',3
--合并处理
--定义结果集表变量
DECLARE @t TABLE(col1 varchar(10),col2 varchar(100))
--定义游标并进行合并处理
DECLARE tb CURSOR LOCAL
FOR
SELECT col1,col2 FROM tb ORDER BY col1,col2
DECLARE @col1_old varchar(10),@col1 varchar(10),@col2 int,@s
varchar(100)
OPEN tb
FETCH tb INTO @col1,@col2
SELECT @col1_old=@col1,@s=''
WHILE @@FETCH_STATUS=0
BEGIN
IF
@col1=@col1_old
SELECT @s=@s+','+CAST(@col2 as varchar)
ELSE
BEGIN
INSERT @t VALUES(@col1_old,STUFF(@s,1,1,''))
SELECT @s=','+CAST(@col2 as varchar),@col1_old=@col1
END
FETCH tb
INTO @col1,@col2
END
INSERT @t VALUES(@col1_old,STUFF(@s,1,1,''))
CLOSE tb
DEALLOCATE tb
--显示结果并删除测试数据
SELECT * FROM @t
DROP TABLE tb
GO
--3.3.2 使用用户定义函数,配合SELECT处理完成字符串合并处理的示例
--处理的数据
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',1
UNION ALL SELECT 'a',2
UNION ALL SELECT 'b',1
UNION ALL SELECT 'b',2
UNION ALL SELECT 'b',3
GO
--合并处理函数
CREATE FUNCTION dbo.f_str(@col1 varchar(10))
RETURNS varchar(100)
AS
BEGIN
DECLARE @re
varchar(100)
SET
@re=''
SELECT
@re=@re+','+CAST(col2 as varchar)
FROM
tb
WHERE
col1=@col1
RETURN(STUFF(@re,1,1,''))
END
GO
--调用函数
SELECT col1,col2=dbo.f_str(col1) FROM tb GROUP BY col1
--删除测试
DROP TABLE tb
DROP FUNCTION f_str
GO
--3.3.3 使用临时表实现字符串合并处理的示例
--处理的数据
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',1
UNION ALL SELECT 'a',2
UNION ALL SELECT 'b',1
UNION ALL SELECT 'b',2
UNION ALL SELECT 'b',3
--合并处理
SELECT col1,col2=CAST(col2 as varchar(100))
INTO #t FROM tb
ORDER BY col1,col2
DECLARE @col1 varchar(10),@col2 varchar(100)
UPDATE #t SET
@col2=CASE
WHEN @col1=col1 THEN @col2+','+col2 ELSE col2 END,
@col1=col1,
col2=@col2
SELECT * FROM #t
--得到最终结果
SELECT col1,col2=MAX(col2) FROM #t GROUP BY col1
--删除测试
DROP TABLE tb,#t
GO
--3.3.4.1 每组 <=2 条记录的合并
--处理的数据
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',1
UNION ALL SELECT 'a',2
UNION ALL SELECT 'b',1
UNION ALL SELECT 'b',2
UNION ALL SELECT 'c',3
--合并处理
SELECT col1,
col2=CAST(MIN(col2) as varchar)
+CASE
WHEN COUNT(*)=1 THEN ''
ELSE ','+CAST(MAX(col2) as varchar)
END
FROM tb
GROUP BY col1
DROP TABLE tb
--3.3.4.2 每组 <=3 条记录的合并
--处理的数据
CREATE TABLE tb(col1 varchar(10),col2 int)
INSERT tb SELECT 'a',1
UNION ALL SELECT 'a',2
UNION ALL SELECT 'b',1
UNION ALL SELECT 'b',2
UNION ALL SELECT 'b',3
UNION ALL SELECT 'c',3
--合并处理
SELECT col1,
col2=CAST(MIN(col2) as varchar)
+CASE
WHEN COUNT(*)=3 THEN ','
+CAST((SELECT col2 FROM tb WHERE col1=a.col1 AND col2 NOT
IN(MAX(a.col2),MIN(a.col2))) as varchar)
ELSE ''
END
+CASE
WHEN COUNT(*)>=2 THEN ','+CAST(MAX(col2) as
varchar)
ELSE ''
END
FROM tb a
GROUP BY col1
DROP TABLE tb
GO
if not object_id('A') is null
drop table
A
Go
Create table A([id] int,[cname] nvarchar(2))
Insert A
select 1,N'张三' union all
select 2,N'李四' union all
select 3,N'王五' union all
select 4,N'蔡六'
Go
--> -->
if not object_id('B') is null
drop table
B
Go
Create table B([id] int,[cname] nvarchar(5))
Insert B
select 1,N'1,2,3' union all
select 2,N'3,4'
Go
create function F_str(@cname nvarchar(100))
returns nvarchar(100)
as
begin
select @cname=replace(@cname,ID,[cname]) from A where
patindex('%,'+rtrim(ID)+',%',','+@cname+',')>0
return @cname
end
go
select [id],dbo.F_str([cname])[cname] from B
id
cname
-----------
----------------------------------------------------------------------------------------------------
1
张三,李四,王五
2
王五,蔡六
.
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编程论坛 2 个网友回答:
SQL code
DECLARE @STR VARCHAR(8000)
SELECT @STR=ISNULL(@STR+',','')+USERNAME FROM TB
SELECT @STR
.
[华 软 网]
编程论坛 3 个网友回答:
SQL code
DECLARE @TB TABLE([UserID] INT, [LastName] VARCHAR(2), [FirstName]
VARCHAR(2), [UserName] VARCHAR(2))
INSERT @TB
SELECT 1, 'A', 'B', 'C' UNION ALL
SELECT 2, 'A1', 'B1', 'C1' UNION ALL
SELECT 3, 'A2', 'B2', 'C2'
DECLARE @STR VARCHAR(8000)
SET @STR=''
SELECT @STR=@STR+','+[UserName]
FROM @TB
SELECT STUFF(@STR,1,1,'')
.
[华 软 网]
编程论坛 4 个网友回答:
SQL code
--1、sql2000中只能用自定义的函数解决
create table tb(id int, value varchar(10))
insert into tb values(1, 'aa')
insert into tb values(1, 'bb')
insert into tb values(2, 'aaa')
insert into tb values(2, 'bbb')
insert into tb values(2, 'ccc')
go
create function dbo.f_str(@id int) returns varchar(100)
as
begin
declare @str
varchar(1000)
set @str =
''
select @str
= @str + ',' + cast(value as varchar) from tb where id = @id
set @str =
right(@str , len(@str) - 1)
return
@str
end
go
--调用函数
select id , value = dbo.f_str(id) from tb group by id
drop function dbo.f_str
drop table tb
--2、SQL2005中的方法
create table tb(id int, value varchar(10))
insert into tb values(1, 'aa')
insert into tb values(1, 'bb')
insert into tb values(2, 'aaa')
insert into tb values(2, 'bbb')
insert into tb values(2, 'ccc')
go
select id, [value] = stuff((select ',' + [value] from tb t where
id = tb.id for XML path('')) , 1 , 1 , '')
from tb
group by id
drop table tb
--3、使用游标合并数据
create table tb(id int, value varchar(10))
insert into tb values(1, 'aa')
insert into tb values(1, 'bb')
insert into tb values(2, 'aaa')
insert into tb values(2, 'bbb')
insert into tb values(2, 'ccc')
go
declare @t table(id int,value varchar(100))--定义结果集表变量
--定义游标并进行合并处理
declare my_cursor cursor local for
select id , value from tb
declare @id_old int , @id int , @value varchar(10) , @s
varchar(100)
open my_cursor
fetch my_cursor into @id , @value
select @id_old = @id , @s=''
while @@FETCH_STATUS = 0
begin
if @id =
@id_old
select @s = @s + ',' + cast(@value as varchar)
else
begin
insert @t values(@id_old , stuff(@s,1,1,''))
select @s = ',' + cast(@value as varchar) , @id_old = @id
end
fetch
my_cursor into @id , @value
END
insert @t values(@id_old , stuff(@s,1,1,''))
close my_cursor
deallocate my_cursor
select * from @t
drop table tb
|