假设存在如下表：
CREATE TABLE Products (
ProductID int,
ProductName nvarchar (40),
Unit char(2),
UnitPrice money
)
表中数据如下：
insert Products
select 1,'产品1','包', 9.9 union all
select 2,'产品2','箱', 20 union all
select 2,'产品2','箱', 20 union all
select 3,'产品3','件', 5 union all
select 4,'产品4','桶', 100 union all
select 4,'产品4','桶', 100 union all
select 4,'产品4','桶', 100
1、在表中增加自增长字段
alter table products add p_id int IDENTITY(1,1)
delete from products where p_id not in (select max(p_id) from products group by ProductID)
alter table products drop column p_id
2、 利用临时表删除表中数据
select distinct * into #temp from products
truncate table products
insert into products select * from #temp
drop table #temp