Example PostgreSQL CTE

CityCountry

CREATE TABLE t (country text, city text, ... other fields);
--
SELECT avg(b.countcountry)::int as "CountryCount", b.country, a.city, count(a.city) as "CityCount"
FROM t AS a
INNER JOIN
(SELECT COUNT(country) AS countcountry, country FROM t GROUP BY country) AS b
ON a.country = b.country
GROUP BY b.country, a.city
ORDER BY 1 DESC,4 DESC;
--
WITH CountryCount AS (
     SELECT COUNT(country) as countcountry,
            country
            FROM t
            GROUP BY country
    ),      
    CityCount AS (
    SELECT COUNT(city) as "CityCount",
           city,
           country
           FROM t
           GROUP BY country, city
    )
    SELECT b.countcountry AS "CountryCount",
         b.country,
         a.city,
         a."CityCount"
    FROM CityCount as a
    INNER JOIN
    CountryCount AS b
    ON a.country = b.country
    ORDER BY b.countcountry DESC,
            a.city DESC
;