Count if field is empty (null)

[michak80]

Hello,

I have a following table: 

LOCATION ID	LOCATION TYPE
LOCATION 1	TEMP
LOCATION 2	TEMP
LOCATION 3	OUT
LOCATION 4	OUT
LOCATION 5	IN
LOCATION 6	null (empty)
LOCATION 7	null (empty)
LOCATION 8	COP
LOCATION 9	COP
LOCATION 10	XDC
LOCATION 11	XDC
LOCATION 12	XDC

I have a problem with null. I'm using 

Count({<LOCATION_TYPE ={'XDC','TEMP','NULL'}>} distinct LOCATION_ID) and I recieved only TEMP and XDC. What should I do to get also location where LOCATION TYPE is empty? 

[anat]

=Count(DISTINCT {<[Change Order Number]={"=Len(Trim(Check))=0 or Check = 1"}>}[Change Order Number])

Or 

=Count({<Check={"=Len(Trim(Check))=0"} > + <Check={"1"}>}[Change Order Number])

Can you try similar to the above