求教一个sql 查询
表 A
a b c
1 sf t1
2 s t1
3 dd t2
4 dd t3
6 dd t6


现在想一次查询出,每个c类的前2条 , 就是2个t1 ,2个t2 ,.这样的记录 ,c的类别不确定
如果类别确定可以用union 但是类别不确定 如果写?

[解决办法]
在存储过程里通过
insert into #ls select distinct(c) from A
对#ls使用游标也可
[解决办法]

SQL code

declare @A table(a int,  b varchar(2), c nchar(2))insert into @Aselect 1  ,'sf','t1' union all select 2  ,'s','t1' union all select 3  ,'dd','t2' union all select 4  ,'dd','t3' union all select 6  ,'dd','t6' union all select 7  ,'dd','t2' union all select 8  ,'cc','t1' union all select 9  ,'a','t2' union all select 10  ,'s','t2' select * from @A m where a in  (select top 2 a from @A where c=m.c)order by m.c a           b    c----------- ---- ----1           sf   t12           s    t13           dd   t27           dd   t24           dd   t36           dd   t6(6 行受影响)
[解决办法]
C# code
create table tb 
 ( 
 a int, 
 b nvarchar(50), 
 c nvarchar(50), 
 ) 
 insert tb select 1,'sf','t1' 
 insert tb select 2,'s','t1' 
 insert tb select 3,'dd','t2'  
 insert tb select 4,'dd','t3' 
 insert tb select 6,'dd','t6' 
  
  
 select * from tb t where a in 
 (select top 2 a from tb where c=t.c) 
  
 drop table tb 
  
  
 (1 料列受到影) 
  
 (1 料列受到影) 
  
 (1 料列受到影) 
  
 (1 料列受到影) 
  
 (1 料列受到影) 
 a       b                          c 
 ----------- -------------------------------------------------- -------------------------------------------------- 
 1       sf                         t1 
 2       s                          t1 
 3       dd                         t2 
 4       dd                         t3 
 6       dd                         t6 
  
 (5 料列受到影)