create proc p_test
as

select isnull(a.NO,b.NO) NO,
isnull(a.NAME,b.NAME) NAME,
isnull(a.[PRICE（RMB）],0) [PRICE（RMB）],
isnull(b.[PRICE（RMB）],0) [PRICE（USD）],
isnull(D.RATE,1) RATE,
[PRICE（USD-RMB）]=isnull(b.[PRICE（RMB）],0)*isnull(D.RATE,1)-isnull(a.[PRICE（RMB）],0)
from 
( A left join C on c.NO=A.NO left join D on C.NO=D.NO ) full join 
( B left join C on c.NO=B.NO left join D on C.NO=D.NO  ) on A.NO=B.NO

------解决方案--------------------
SQL code
--你的结果是不是错了?
declare @a table(NO INT, NAME VARCHAR(20), [PRICE(RMB)] int)
insert @A select 1 ,'AA', 10
UNION ALL select 2 ,'BB', 20
UNION ALL select 3 ,'CC', 30
declare @B table(NO INT, NAME VARCHAR(20), [PRICE(USD)] int)
insert @B select 1 ,'AA', 20
UNION ALL select 3 ,'CC', 30
UNION ALL select 4 ,'DD', 50


declare @c table(NO INT)
insert @C select 1


declare @d table(NO INT, RATE INT)
insert @d select 1, 6

SELECT ISNULL(A.NO,B.NO) NO,
        ISNULL(A.NAME,B.NAME) NAME,
        ISNULL(A.[PRICE(RMB)],0) [PRICE(RMB)],
        ISNULL(B.[PRICE(USD)],0) [PRICE(USD)],
        ISNULL(RATE,1) RATE,
        ISNULL([PRICE(USD)],0)*ISNULL(RATE,1) [PRICE(RMB-USD)]
 FROM @A A FULL JOIN @B B ON A.NO=B.NO LEFT JOIN @C C ON A.NO=C.NO OR B.NO=C.NO 
LEFT JOIN @D D ON C.NO=D.NO 
ORDER BY 1

--RESULT
/*
NO          NAME                 PRICE(RMB)  PRICE(USD)  RATE        PRICE(RMB-USD) 
----------- -------------------- ----------- ----------- ----------- -------------- 
1           AA                   10          20          6           120
2           BB                   20          0           1           0
3           CC                   30          30          1           30
4           DD                   0           50          1           50

（所影响的行数为 4 行）*/

------解决方案--------------------
楼主的结果不对

------解决方案--------------------
SELECT ISNULL(A.NO,B.NO) NO,
       ISNULL(A.NAME,B.NAME) NAME,
       ISNULL(A.[PRICE(RMB)],0) [PRICE(RMB)],
       ISNULL(B.[PRICE(USD)],0) [PRICE(USD)],
       ISNULL(RATE,1) RATE,
       ISNULL([PRICE(USD)],0)*ISNULL(RATE,1) [PRICE(RMB-USD)]
  FROM A FULL JOIN  B ON A.NO = B.NO  
     LEFT JOIN C ON A.NO = C.NO OR B.NO = C.NO  
     LEFT JOIN D ON C.NO = D.NO