Distinct count for null fields

[Anoop91]

Hi Everyone ,

Im trying to get the distinct count of null values , For the below data set , I want to get the Count of Case ID where Standardized Issue is Blank or Null 

I used "NullCount([Standardized Issue:]) " and it throws the count as 4 , but the unique count is only "2"

I tried "NullCount(distinct([Standardized Issue:]))" and it throws the count as "1"

can someone please help me with this formulation 

Case ID	Standardized Issue:	SKU
CASE-19647	MATERIAL SHORTAGE	ABCD1234
CASE-19647	MATERIAL SHORTAGE	ABCD2345
CASE-19647	MATERIAL SHORTAGE	ABCD3456
CASE-19647	MATERIAL SHORTAGE	ABCD4567
CASE-19647	MATERIAL SHORTAGE	ABCD5678
CASE-19647	MATERIAL SHORTAGE	ABCD6789
CASE-19647	MATERIAL SHORTAGE	ABCD7900
CASE-19603		ABCD9011
CASE-19603		ABCD10122
CASE-19647	TOOLING DOWN	ABCD11233
CASE-19647	TOOLING DOWN	ABCD12344
CASE-19567	COSTING TO BE WORKED	ABCD13455
CASE-19561		ABCD14566
CASE-19561		ABCD15677

[Anoop91]

Thank you , this works !