Show only once

[mypeljo]

I have a query consisting of the fields productid and customerid.It shows the products bought by the customers.These products are bought with different orders.Therefore they are repeated many times for one and the same customerid. I want to show however only the clients that have bought this product.Therefore is it possible to restrict the query and show the customerid for a given productid only once.
For example

Productid customerid

1409 3000
1409 3000
1409 3000
1409 3000

Is it possible for the query to show only:
1409 3000

 

[Golom]

Try

Select DISTINCT productid, customerid
From ...
[blue]...etc. ...[/blue]