Sample of data:

CustomerID | OrderAmount | RegionID
10001      |     50      |   801
10002      |     25      |   801
10003      |     200     |   802
10001      |     100     |   802
10002      |     20      |   802
...

And my expected result is:

RegionID  |  CategoryID  |  Num_of_Sales
801       |      1       |     2          -----Below 100
801       |      2       |     0          -----100-200
802       |      1       |     2          -----Below 100
802       |      2       |     1          -----100-200
...