How to get Order_ID that don't have connection between 2 table?

[#1]

How to make expression to get Order_ID that don't have connection between 2 table?

If i have Table A (contains ORDER_ID, SALES_ID) and table B (contains ORDER_ID, VALUE).

I want to get count(ORDER_ID) by dimension SALES_ID, but i don't want to get ORDER_ID have connection between 2 tables.

Can someone help me to make expression?

[Jason_Michaelides · Accepted solution]

Try:

Count(DISTINCT If(IsNull(VALUE),ORDER_ID))

How this helps,

Jason

[#3]

Thanks