xml类型数据处理层次数据，with递归也能处理层次数据

/*表结构，数据如下：
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(在sql server 2000中只能用函数解决。)
--======================================================
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
--1. 创建处理函数
CREATE FUNCTION dbo.f_strUnite(@id int)
RETURNS varchar(8000)
AS
BEGIN
    DECLARE @str varchar(8000)
    SET @str = ''
    SELECT @str = @str + ',' + value FROM tb WHERE id=@id
    RETURN STUFF(@str, 1, 1, '')
END
GO
-- 调用函数
SELECt id, value = dbo.f_strUnite(id) FROM tb GROUP BY id
drop table tb
drop function dbo.f_strUnite
go
/*
id          value
----------- -----------
1          aa,bb
2          aaa,bbb,ccc
（所影响的行数为 2 行）
*/
--======================================================
2. 新的解决方法(在sql server 2005中用OUTER APPLY等解决。)
-- 查询处理
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
            ), ' ', ','), '"/>', ''), 1, 1, '')
)N
drop table tb

/*
id          values
----------- -----------
1          aa,bb
2          aaa,bbb,ccc

(2 行受影响)
*/

--SQL2005中的方法2
select id, [values]=stuff((select ','+[value] from tb t where id=tb.id
for xml path('')), 1, 1, '')
from tb
group by id
/*
id          values
----------- --------------------
1          aa,bb
2          aaa,bbb,ccc
*/
3.--SQL2005中的方法 with递归

with roy as(select id,value,row=row_number()over(partition by id order by id) from tb)
,Roy2 as
(select id,cast(value as nvarchar(100)) value,row from Roy where row=1
union all
select a.id,cast(b.value+','+a.value as nvarchar(100)),a.row from Roy a join Roy2 b on a.id=b.id and a.row=b.row+1)
select id,value from Roy2 a where row=(select max(row) from roy where id=a.id)

/*有表tb, 如下:
id          value
----------- -----------
1          aa,bb
2          aaa,bbb,ccc
欲按id,分拆value列, 分拆后结果如下:
id          value
----------- --------
1          aa
1          bb
2          aaa
2          bbb
2          ccc */

1. 旧的解决方法(sql server 2000)
create table tb(id int,value varchar(30))
insert into tb values(1,'aa,bb')
insert into tb values(2,'aaa,bbb,ccc')
go

select a.id, substring(a.[value], b.number, charindex(',', a.[value] + ',', b.number) - b.number)
FROM tb a, (select number from master..spt_values where type='p' )b ---b表保存1到2048的常量
WHERE substring(',' + a.[value],b.number, 1) = ','

2. 新的解决方法(sql server 2005)

SELECT a.id, b.value
FROM(
    SELECT id, [value] = CONVERT(xml,' ' + REPLaCE([value], ',', ' ') + ' ') FROM tb
)a
OUTER aPPLY(
    SELECT value = N.v.value('.', 'varchar(100)') FROM a.[value].nodes('/root/v') N(v)
)b

DROP TabLE tb

/*
id          value
----------- ------------------------------
1          aa
1          bb
2          aaa
2          bbb
2          ccc

(5 行受影响)
*/

3.--SQL2005中的方法 with递归
with roy as
(select id,value=cast(left(value,charindex(',',value+',')-1) as nvarchar(100)),Split=cast(stuff(value+',',1,charindex(',',value+','),'') as nvarchar(100)) from #Tb
union all
select id,value=cast(left(Split,charindex(',',Split)-1) as nvarchar(100)),Split= cast(stuff(Split,1,charindex(',',Split),'') as nvarchar(100)) from Roy where split>''
)
select id,value from roy

ITPub博客

字符串合并分拆

最新文章