RELATEDTABLE and distinct

[msprog]

HI,
I need some help here.

I have a simple powerbi model with 2 tables, Product and Sales.

The Sales table has fields: OrderNo, LineNo, ProductKey , Qty, etc
The Product table has ProductKey, ProductName, Description.

There is a 1 to Many relationship between Product and Sales table.

Now, On the Product table, in powerBI, i want to have a calculated Column called NumberofOrders.
NumberofOrders is the distinct count orders in which the product has been sold. Remeber a Product may appear more than one line items within an order, hence only the distinct count of orders.

How can i achieve this? I know we need to use RELATEDTABLE.

I am trying something like

=COUNTROWS(distinct(RELATEDTABLE(FactInternetSales)))

but this doesn't work/

Hww do i use a distinct in this case?
Please help
thanks

[vik0810 · Accepted solution]

Hi @msprog,

you can use following DAX:

NumberOfOrders = CALCULATE(DISTINCTCOUNT(sales[OrderNo]), RELATEDTABLE(sales))

[msprog]

Hi @vik0810

I have a followup question on this if it is ok. 

NumberOfOrders = CALCULATE(DISTINCTCOUNT(sales[OrderNo]), RELATEDTABLE(sales))

The solution works fine but as i am reading more about PowerBI , a question arose  on the use of RelatedTable function in this solution, which i am hoping the  you/community can help clarify.  I am wondering why the below code is not working:

NumberOfOrders = CALCULATE(DISTINCTCOUNT(sales[OrderNo]), sales)

why do we need the RelatedTable when we are using Calculate?

THis is my thinking:

I read that the Calculate function converts Row into a filter context and the filter context filters the whole model based on the realtionships.  So we have a 1 to many relationship between Product and Sales.  we are creating a calculated column in Product.  So there is a row context.  Now the use of Calculate should convert the row context into filter, which means the Sales table should get filtered, automatically?  Please help clarify

thanks