Find rows in lookup table that don't match any row in the data table

[unire]

What's the best way (preferably with DAX query functions, such as SUMMARIZE, GENERATE, etc) to find all the rows in a lookup table that have no matching row in the data table?

For example, with a data table like this:

Person ID	Country Key	Age
581	1	25
492	1	48
390	2	37
410	2	29
173	2	61

<tbody>
</tbody>

And this lookup table:

Country Key	Country Name
1	United Kingdom
2	Japan
3	China

<tbody>
</tbody>

The query would need to return one row (3 - China).

 

[unire]

I think I figured it out.
To get all the rows in the lookup table that don't match any row in the data table, I'm doing this:

EVALUATE
FILTER(
DimCountries,
COUNTROWS(RELATEDTABLE(FactPeople)) = 0
)

And to do the other way around (data rows that don't match a lookup row):

EVALUATE
FILTER(
FactPeople,
RELATED(DimCountries[Country Key]) = BLANK()
)

But I don't know whether there are more efficient solutions.