用SUM()函数实现交叉数据报表

1 用SUM()函数实现交叉数据报表：
有下面的数据:

Col1            Col2        col3
AAAA          aaaa        2
AAAA          bbbb       5
AAAA          cccc        6
BBBB           aaaa        3
BBBB           dddd        2
CCCC           bbbb       3
CCCC           dddd       2

如何用SQL 转换成下面的形式:

                              AAAA          BBBB           CCCC
aaaa                        2                  3                0
bbbb                       5                                    3               
cccc                        6
dddd                                           2                2
实现:
select col2, SUM(decode(col1,'AAAA',COL3,NULL)) AAAA,
     SUM(decode(col1,'BBBB',COL3,NULL)) BBBB,
     SUM(decode(col1,'CCCC',COL3,NULL)) CCCC
FROM TEST1
GROUP BY COL2;