日期:2014-05-18  浏览次数:20539 次

数据库部分列相同合并的sql语句的写法
如:
create table test1(ID int identity(1,1),code nvarchar(20) not null)
create table test2(ID int identity(1,1),inttest1ID int not null,
nvcID nvarchar(10) not null)
create table test3(nvcID nvarchar(10) not null,
nvcName nvarchar(20) not null) 
insert into test1(code) values('002')
insert into test2(nvcID,inttest1ID) values('01',1)
insert into test2(nvcID,inttest1ID) values('02',1)
insert into test3(nvcID,nvcName) values('01','yin')
insert into test3(nvcID,nvcName) values('02','wang')

现查询:
select a.ID,a.code,b.nvcID,c.nvcName
 from test1 a 
 left join test2 b on a.ID=b.inttest1ID left join test3 c on b.nvcID=c.nvcID
结果:
1 002 01 yin
1 002 02 wang
假如我想要的结果为:
1 002 01,02 yin,wang

即将第三列和第四列合并在一起(如果前面两列相同)
请问这样的sql语句应该如何写?


------解决方案--------------------
SQL code
合并列值 
--*******************************************************************************************
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。) 
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 
-- 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 
            ), ' <N value="', ','), '"/>', ''), 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 
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, [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 

(2 row(s) affected) 

*/ 

drop table tb