같은 날짜에 단가가 2번 들어오지는 않겠죠?

2005버전 이상이라면 ROW_NUMBER()를 이용하는 방법은 어떨까요

WITH 테이블

AS

(

    SELECT 1 AS seq, '매출' AS 구분, '2015.02.13' AS 날짜, '품목1' AS 품목, 1 AS 수량, 100 AS 단가

    UNION ALL

    SELECT 2, '매출', '2015.02.13', '품목2', 2, 150

    UNION ALL

    SELECT 3, '매입', '2015.02.13', '품목3', 5, 200

    UNION ALL

    SELECT 4, '매출', '2015.02.13', '품목3', 3, 300

    UNION ALL

    SELECT 5, '매출', '2015.02.11', '품목2', 1, 100

    UNION ALL

    SELECT 6, '매출', '2015.02.12', '품목2', 2, 200

)

(

    SELECT  A.품목

            , A.단가

            , A.날짜

    FROM

    (    

        SELECT  품목

                , 단가

                , 날짜

                , ROW_NUMBER() OVER(PARTITION BY 품목 ORDER BY 날짜 DESC )  AS RowNum

        FROM    테이블

        WHERE   구분 = '매출'

    )   AS A

    WHERE A.RowNum = 1

)

select *

from ( select cDate, cProduct, max(cSeqNo) as cSeqNo from dbo.tSales where cGroup = '매출' group by cDate, cProduct ) as a

join dbo.tSales as b on b.cSeqNo = a.cSeqNo