[StrataScractch] Number Of Units Per Nationality [MySQL]

https://platform.stratascratch.com/coding/10156-number-of-units-per-nationality?code_type=3 

StrataScratch

 

WITH UNDER_30 AS (
    SELECT DISTINCT(host_id), nationality
    FROM airbnb_hosts
    WHERE age < 30
)
select nationality, COUNT(*) 
FROM UNDER_30 
LEFT OUTER JOIN airbnb_units 
ON airbnb_units.host_id = UNDER_30.host_id
WHERE airbnb_units.unit_type = "apartment"
GROUP BY nationality
ORDER BY COUNT(*) DESC;