Hi,

I understand what you are trying to do, I did some research and testing.
I've learned something, your combination distinct and count on a field doesn't seem to work in Access but in an sql-server database it seems to work.

I've learned something.
I've said that with a count you always need a group by ... this is wrong apparently. If you only want to count some records using 1 field it's no problem. ex.

 
select count(Name)
from table where age = 29
In your case, your first statement would work in an sql-server like this:

 
SELECT count (distinct Subject_Area.Subject_Area_Name) as number, 
FROM Data_Model, (Subject_Domain INNER JOIN Subject_Area ON Subject_Domain.Subject_Domain_ID = Subject_Area.Subject_Domain
or with the domain_name=> number of distinct areas for each domain:

SELECT count (distinct Subject_Area.Subject_Area_Name) as number, Subject_Domain.Subject_Domain_Name
FROM Data_Model, (Subject_Domain INNER JOIN Subject_Area ON Subject_Domain.Subject_Domain_ID = Subject_Area.Subject_Domain
group by Subject_Domain.Subject_Domain_Name
Are you using access?

If this feedback helps to solve the issue, let me know the outcome. Interesting case.