8_sql_solution

WITH quantity_cust_sex AS(
    SELECT country_name,
        cust_gender,
        COUNT(cust_gender) AS quantity
    FROM sh.customers
    JOIN sh.countries ON sh.customers.country_id = sh.countries.country_id
    GROUP BY country_name, cust_gender)
SELECT country_name AS "Страна",
    round((SELECT quantity
        FROM quantity_cust_sex q2
        WHERE q1.country_name = q2.country_name
        AND cust_gender = 'M'
        ) / ( SELECT SUM(quantity)
            FROM  quantity_cust_sex q2
            WHERE q1.country_name = q2.country_name
        ) * 100, 2) AS "% мужчин",
    round((SELECT quantity
        FROM quantity_cust_sex q2
        WHERE q1.country_name = q2.country_name
        AND cust_gender = 'F'
        ) / ( SELECT SUM(quantity)
            FROM  quantity_cust_sex q2
            WHERE q1.country_name = q2.country_name
        ) * 100, 2) AS "% женщин"
FROM quantity_cust_sex q1
GROUP BY country_name
ORDER BY country_name
;