Задача 23

WITH
avg AS (
    SELECT
        AVG(funding_total) AS avg_total,
        country_code AS country,
        EXTRACT(YEAR FROM CAST(founded_at AS DATE)) AS years
    FROM
        company
    GROUP BY
        country_code,
        years
)

SELECT
    a1.country,
    a1.avg_total AS avg2011,
    a2.avg_total AS avg2012,
    a3.avg_total AS avg2013
FROM
    avg AS a1
    INNER JOIN avg AS a2 ON a2.country = a1.country
    INNER JOIN avg AS a3 ON a3.country = a1.country
WHERE
    a1.years = 2011
    AND a2.years = 2012
    AND a3.years = 2013
ORDER BY
    avg2011 DESC