I'm storing data in two tables (TblOrder and TblClient).
OrderNo Client Date
1 A 2010
2 B 2010
3 A 2010
4 C 2010
5 D 2011
6 E 2011
I'm trying to find out how to find the number of unique clients that placed an Order during a specific Date (from TblOrder) and are from a specific country (from TblClient).
The number of UNIQUE clients that placed an order during 2010 AND are from country A?
Answer: equals to 2 unique clients.