Unique count

I'm trying to do a unique count of records that use a combination of fields (email, store). The basic count function in Knack is not enough for me. I'm not a proficient coder. Any ideas of what I could use or example code would be greatly appreciated. Thanks!

I think this is what Beth wants to do:

For a table with email, store, item. A given customer with email customer@test.com shops at two stores and buys multiple items at each. There is a record for each item bought.


customer@test.com storeA item1

customer@test.com storeA item2

customer@test.com storeB item1

customer@test.com storeB item2

customer@test.com storeB item3

How can I return a 2 for storeA and a 3 for storeB? Is that something the sum field/filter can do?