declare  @table1 table (id int,price int,starttime datetime, orderid int)
insert into @table1
select 1,50,'2012-5-1',1
union select  2,100,'2012-5-1',1
union select  3,50,'2012-5-1',2
union select  4,60,'2012-5-1',2
union select  5,70,'2012-5-1',2
union select  6,70,'2012-5-1',3
union select  7,90,'2012-5-1',3 ;
with
a as 
(
   select orderid,max(price) as maxprice from @table1 group by orderid
)
select [@table1].* from @table1,a where [@table1].orderid = a.orderid and [@table1].price = a.maxprice

declare  @table1 table (id int,price int,starttime datetime, orderid int)
insert into @table1
select 1,50,'2012-5-1',1
union select  2,100,'2012-5-1',1
union select  3,50,'2012-5-1',2
union select  4,60,'2012-5-1',2
union select  5,70,'2012-5-1',2
union select  6,70,'2012-5-1',3
union select  7,90,'2012-5-1',3 
union select  8,90,'2012-5-1',3 
;
--1
SELECT * FROM @table1 a WHERE NOT EXISTS(SELECT 1 FROM @table1 b WHERE a.orderid=b.orderid AND a.price<b.price)
--
SELECT * FROM @table1 a WHERE NOT EXISTS(SELECT 1 FROM @table1 b WHERE a.orderid=b.orderid AND a.price<b.price OR (a.orderid=b.orderid  AND a.id<b.id))

--2
SELECT * FROM @table1 a WHERE 1>(SELECT COUNT(*) FROM @table1 b WHERE a.orderid=b.orderid AND a.price<b.price)

--3
;WITH t AS
(
SELECT *,row=ROW_NUMBER()OVER(PARTITION BY orderid ORDER BY price DESC) FROM @table1
)
SELECT * FROM t WHERE row=1