求教！！sql语句过滤两个字段重复值

[zxaibulams]

现有表结构
create table abc (A char(2),B char(2),C char(2))
插入数据
insert abc values("a1","b1","c1")
insert abc values("a1","b1","c2")
insert abc values("a2","b2","c1")
insert abc values("a2","b2","c2")
insert abc values("a3","b3","c2")
insert abc values("a3","b3","c2")
现想获得数据
a1,b1
a2,b2
a3,b3
即过滤掉前两字段的重复值,请问sql语句改怎么写

[letqqqgo]

select distince a,b from 表
即可

[intotheheart]

select distinct a.b from table

[zxaibulams]

select distince a,b from 表
是过滤掉a重复,这样范围就缩小了
insert abc values("a1","b1","c1")
insert abc values("a1","b1","c2")
insert abc values("a2","b2","c1")
insert abc values("a2","b2","c2")
insert abc values("a3","b3","c2")
insert abc values("a3","b3","c2")
再加一条
insert abc values("a2","b3","c2")
那么应该显示
a1,b1
a2,b2
a2,b3
a3,b3

[zqz117]

select distince a,b from 表

确实会显示
a1,b1
a2,b2
a2,b3
a3,b3
难道这有什么不对吗？