How to calculate sum of single value from related table

[Z7_852]

I have three tables: [Category] that has relationship to [Purchase] that has relationship to [Customer]. All relationships are one to many.

Now I want to calculate number of customers that have bought only from specific category "B".

Doing a simple Calculate(DISTINCTCOUNT(Customer[Id], Filter[Category, Category[type] = "B") returns all sales from said category. I want to know number of customers who have only bought from this one category (once or more times).

Example

Customer	Purchase	Category
1	100	B
1	101	B
2	102	A
2	103	B
3	104	B
4	105	C

This should return 2 because Customers 1 and 3 have bought only "B". Where as now it returns 3 because client 2 have also bought "B" as well as "A".

[v-zhangti · Accepted solution]

Hi, @Z7_852 

You can try the following methods.

Measure:

Count1 = CALCULATE(DISTINCTCOUNT(Purchase[Category]),ALLEXCEPT(Customer,Customer[Customer]))

Count result = 
Var _table=CALCULATETABLE(VALUES(Customer[Customer]),FILTER(ALL(Customer),[Count1]=1))
Return
CALCULATE(DISTINCTCOUNT(Customer[Customer]),FILTER(ALL(Category),[Category]="B"),FILTER(ALL(Customer),[Customer] in _table))

Is this the result you expect? Please see the attached document.

Best Regards,

Community Support Team _Charlotte

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

[Dangar332]

HI, @Z7_852 

try below

Measure = 

 CALCULATE(DISTINCTCOUNT(Customer[Id]),
       FILTER( 
          ADDCOLUMNS(
             ALL('Customer[Id]),
             "countofcategory",CALCULATE(DISTINCTCOUNT(Category[type]))
          ),
         [d]<2
        ),
        Category[type] = "B"
  )