declare @A table(ccode int,cdate datetime,cmoney int)
insert into @A
select 801,'2012-08-01',120 union all
select 801,'2012-08-05',110 union all
select 801,'2012-08-10',100 union all
select 802,'2012-07-01',80 union all
select 802,'2012-08-10',60 union all
select 803,'2012-08-06',86
declare @B table(ccode int,selldate datetime,sellmoney int)
insert into @B
select 801,'2012-08-01',130 union all
select 801,'2012-08-02',130 union all
select 801,'2012-08-08',150 union all
select 801,'2012-08-11',120 union all
select 802,'2012-08-12',100 union all
select 803,'2012-08-13',100
select t.*,sellmoney-cmoney as 毛利
from 
(
    select b.*,(select top 1 cmoney from @A a where a.ccode=b.ccode and datediff(day,a.cdate,b.selldate)>=0 order by a.cdate desc) cmoney  from @B b
) t

/*
ccode       selldate                sellmoney   cmoney      毛利
----------- ----------------------- ----------- ----------- -----------
801         2012-08-01 00:00:00.000 130         120         10
801         2012-08-02 00:00:00.000 130         120         10
801         2012-08-08 00:00:00.000 150         110         40
801         2012-08-11 00:00:00.000 120         100         20
802         2012-08-12 00:00:00.000 100         60          40
803         2012-08-13 00:00:00.000 100         86          14
*/

------解决方案--------------------
用一下上在老兄数据。
;WITH cte AS (
	SELECT b.ccode,a.cmoney,b.sellmoney,rr=ROW_NUMBER() OVER(PARTITION BY b.rn ORDER BY ABS(datediff(dd,a.cdate,b.selldate))) FROM @a a join
	(SELECT rn=ROW_NUMBER() OVER(ORDER BY GETDATE()),* FROM @b) b  
	ON a.ccode=b.ccode
)
SELECT *,sellmoney-cmoney  FROM cte  WHERE rr=1;
/*
ccode       cmoney      sellmoney   rr                  
----------- ----------- ----------- -------------------- -----------
801         120         130         1                    10
801         120         130         1                    10
801         100         150         1                    50
801         100         120         1                    20
802         60          100         1                    40
803         86          100         1                    14
*/

------解决方案--------------------
SQL code
SELECT  t.*, sellmoney - cmoney AS 毛利
FROM    (
          SELECT  b.* ,
                  (
                    SELECT TOP 1
                            cmoney
                    FROM    ta a
                    WHERE   a.ccode = b.ccode
                            AND DATEDIFF(day, a.cdate, b.selldate) >= 0
                    ORDER BY a.cdate DESC
                  ) cmoney
          FROM    tb b
        ) t

------解决方案--------------------
探讨

SQL code
declare @A table(ccode int,cdate datetime,cmoney int)
insert into @A
select 801,'2012-08-01',120 union all
select 801,'2012-08-05',110 union all
select 801,'2012-08-10',100 union all
se……