---

SELECT
    car.marka,
    car.model,
    COUNT(dogovor.id_dogovor) AS `Количество договоров`,
    ROUND(
        COALESCE(
            SUM(
                car.cena * 0.001 *
                DATEDIFF(dogovor.data_vozvrata, dogovor.data_vidachi)
            ),
            0
        ),
        2
    ) AS `Суммарная стоимость договоров`,
    ROUND(
        COALESCE(
            AVG(
                DATEDIFF(dogovor.data_vozvrata, dogovor.data_vidachi)
            ),
            0
        ),
        2
    ) AS `Средняя длительность аренды`
FROM car
LEFT JOIN dogovor
    ON car.id_car = dogovor.id_car
GROUP BY
    car.id_car,
    car.marka,
    car.model,
    car.cena
ORDER BY
    `Суммарная стоимость договоров` DESC;