Oracle中 GROUP BY 与 INNER JOIN 连用, 且GROUP BY 中加入条件

SELECT * 
FROM(SELECT
FULLCODE, 
KCRQ, 
COUNT(CASE WHEN MRJJ>0 THEN MRJJ ELSE NULL END ) AS BUYCOUNT, 
SUM(CASE WHEN MRJJ>0 THEN MRJJ ELSE NULL END ) AS BUYAMOUNT, 
COUNT(CASE WHEN MCJJ>0 THEN MCJJ ELSE NULL END ) AS SELLCOUNT, 
SUM(CASE WHEN MCJJ>0 THEN MCJJ ELSE NULL END ) AS SELLAMOUNT
FROM Mncg_Stg_CC GROUP BY FULLCODE, KCRQ )A 
INNER JOIN (SELECT FULLCODE, STKCOD FROM MNCG_STG_STKIDMAP) B
ON A.FULLCODE = B.FULLCODE