DAX to count when no value is related

[M_Donovan]

Hi all

I am struggling to get my head around something that i am sure is simple in Excel power pivot data model.

Table A has X_Id 

Table B has X_Id and Y_id

not all items from A are in B but all items in B (X_id) are in A (1 to many). This has been set up as a relationship 

I want to get a measure that will give me counts for all the X_IDs in Table A that are not in Table B i.e dont have a Y_id.

hopes that makes sense and thanks in advance

Mike

[M_Donovan]

Johnt,

Seems do do exactly what i wanted to. 

Thanks

Mike

[johnt75 · Accepted solution]

Try

Missing from B =
COUNTROWS ( EXCEPT ( VALUES ( 'TableA'[X id] ), VALUES ( 'TableB'[X id] ) ) )