how to count the numbers for "group by"
I have a POS list as follows:
Customer product ship_month qty amt
Cust_A Product_A 1 50 100
Cust_A Product_A 1 100 200
Cust_B Product_A 1 50 80
my question is , how to konw how many customers buy the Product_A monthly. for examples, I get the report
Product Cust_CNT month Qty_total amt_total
ProductA 2 1 200 380
I use the summary based count, it get the "3", it is not correct numbers. how to count the number group by customer.