sql 选取每个分组中的第一条数据

--1.创建测试表
Create Table #Order1
(
OrderName varchar(50),
RequestDate datetime,
OrderCount int
)
-- 插入测试数据
insert into #Order1 values(\'衣服\',\'2013-06-02\',2)
insert into #Order1 values(\'衣服\',\'2013-06-03\',4)
insert into #Order1 values(\'衣服\',\'2013-06-04\',5)

insert into #Order1 values(\'鞋\',\'2013-06-02\',3)
insert into #Order1 values(\'鞋\',\'2013-06-03\',7)
insert into #Order1 values(\'鞋\',\'2013-06-04\',8)

--选取每组中时间最近的一条

-- 方法1

select * from
(
select ROW_NUMBER()over(PARTITION By OrderName ORDER BY RequestDate DESC) as rownum, OrderCount,OrderName
from #Order1
) T
where T.rownum = 1

--group by OrderName
drop table #Order1

--未完待续