group by语句加流水号的问题2

[tjm1]

表有a, b, c三个字段，数据如下：

A B C
---------------
A A 1
A B 2
B A 3
B A 4
C A 1

要求对a, b字段分组，对c求和，实现如下效果：

序号 A B C
-------------------
1 A A 1
1 A B 2
2 B A 7
3 C A 1

上面的序号(流水号)怎么实现，用一句sql？就是说A字段内容一样，序号也一样

[临摹]

CREATE TABLE TABLE1(A VARCHAR2(10),B VARCHAR2(10),C VARCHAR2(10));
INSERT INTO TABLE1 VALUES('A','A','1');
INSERT INTO TABLE1 VALUES('A','B','2');
INSERT INTO TABLE1 VALUES('B','A','3');
INSERT INTO TABLE1 VALUES('B','A','4');
INSERT INTO TABLE1 VALUES('C','A','1');
COMMIT;

SELECT RN,T1.A,T1.B,T1.C FROM
(SELECT T1.A,T1.B,SUM(T1.C) C FROM TABLE1 T1 GROUP BY A,B)T1,
(SELECT ROWNUM RN,A FROM(SELECT A FROM TABLE1 GROUP BY A)) T2
WHERE T1.A=T2.A;

RN A B C
---------- ---------- ---------- ----------
1 A A 1
1 A B 2
2 B A 7
3 C A 1