筛选分组的第一条记录

SELECT     *

FROM         (SELECT    
A.a
,A.b
,A.c

,A.d, ROW_NUMBER() 

                                              OVER (partition BY
A.a 

                       ORDER BY A.b  DESC) AS
bz

FROM        A

GROUP BY
A.a ,A.b ,A.c ,A.d )
a
WHERE    
bz <= 1

强行套用成功，具体含义还需进一步研究