分类: 数据库开发技术
2006-06-13 13:29:05
create table abc(
i nvarchar(10),
ii int,
iii int,
iiii int,
price money)
go
insert into abc
select 'b',1,2,1,11
union all
select 'b',211,2,1,211
union all
select 'a',21,2,1,311
union all
select 'd',41,42,1,411
union all
select 'd',41,42,1,511
union all
select 'd',41,42,1,611
union all
select 'e',1,2,1,11
union all
select 'e',71,2,1,31
union all
select 'e',61,2,1,911
union all
select 'e',771,2,1,1
go
要求的结果是:
以i分组,求每组price最大的前2条记录
i ii iii iiii price
---------- ----------- ----------- ----------- ---------------------
a 21 2 1 311.0000
b 1 2 1 11.0000
b 211 2 1 211.0000
d 41 42 1 511.0000
d 41 42 1 611.0000
e 71 2 1 31.0000
e 61 2 1 911.0000
1.
select *
from abc a
where (
select count(*) from abc b
where a.i=b.i and b.price>a.price)<2
order by i,price
连接查询,判断数量
2.
select i,ii,iii,iiii,price
from (
select (select isnull(sum(1),0)+1 from abc b where a.i=b.i and a.price
where ids<3
order by i,price
生产一个内部表,给内部表tem中的每一组排序,并把排序号放入新列ids中
3.
declare @looptime int
declare @count int
declare @i nvarchar(10)
/*定义表变量@abc,和表ABC中的所有列类型相同*/
declare @abc table(
i nvarchar(10),
ii int,
iii int,
iiii int,
price money)
declare @tem table(
ids int identity,
class nvarchar(10))
/*把表ABC中的所有组全部查询出来,暂时存在表变量@tem中*/
insert into @tem(class)
select i
from abc
group by i
/*求出表变量@tem中行数量*/
select @count=@@rowcount
/*循环变量@looptime赋初值=1*/
select @looptime=1
while(@looptime<)
begin
/*将每组名赋值到变量@i*/
select @i=class
from @tem
where
/*将每组前2名插入到表变量@abc中*/
insert into @abc
select top 2 *
from abc
where
order by price desc
/*循环变量@looptime累加1*/
select @looptime=@looptime+1
end
/*显示结果*/
select *
from @abc
order by i,price
4.
用游标来处理
方法和我的第3种方法类似,大家可以自己试试
我共写了4种,不知道大家还有什么其他好方法,可以交流,谢谢。