Counting unique customers per day, week, month, year..

Is there are some oracle features that allow me to do this?

e.g.
let's say i have a table
orders:
product_id, customer_id, date

1	10	01-01-2005
2	10	01-02-2005
1	12	01-01-2005
4	13	01-04-2005

product_groups
product_id	group_id
1		2
2		2
4		1

.. you get the idea

I'd like to figure out
unique customers per product per date
unique customers per product per month
unique customers per product per year
unique customers per product_grou per date

Basically, just b/c you have 100 unique customers on jan 1, and 100 unique customers on jan 2nd, doesn't mean that you have 200 unique customers between those 2 dates, and you'd have to come up with different queries to figure this out, but since there are so many possible combinations (e.g. you can add other attributes to products besides groups, like order came through partner), I figured there has to be some features to help us out.

Thanks.
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We use Oracle 8.1.7.4 and 9.2.0.5 on Solaris 2.7 boxes remove NSPAM to email Received on Fri Apr 15 2005 - 16:50:24 CDT