SQL & PL/SQL

[SQL] how can i get this result....??(accumulation distinct count)

Hi everybody,

pls tell me how can it possible to get result?

### sample data

date visitor
----- ------
10-01 A
10-01 A
10-01 B
10-01 B
10-01 C
10-01 C
10-02 A
10-02 C
10-02 C
10-02 D
10-02 D
10-03 B
10-03 B
10-03 B
10-03 A
10-03 A
10-03 F
10-04 A
10-04 A
10-04 F


result that i want...like this.


date date_unqiue_visitors acc_date_unique_visitors
----- ------------- --------------------
10-01 3 3
10-02 3 4
10-03 3 5
10-04 2 5



date distinct visitors : count(distinct visitor)

but how can i get accumulation distinct visitor count???

Thanks to every body..