是否要查找超过目的地平均金额的预订？

SELECT b.*
FROM booking b
    INNER JOIN (
        -- Make a subquery (think of it as a helper table) to look up the average booking amount for each destination.
        SELECT destination_id, AVG(book_amount) AS book_amount_avg FROM booking GROUP BY destination_id
    ) AS da
        ON b.destination_id = da.destination_id
WHERE b.book_amount > da.book_amount_avg

那么这个怎么样？

SELECT d.destination_id, d.name
FROM destination d
    INNER JOIN (
        -- Total value bookings for each destination.
        SELECT destination_id, SUM(booking_amount) AS booking_amount_destination_sum 
        FROM booking 
        GROUP BY destination_id
    ) AS dt
        ON d.destination_id = dt.destination_id
    INNER JOIN (
        -- Averave value of bookings for each location.
        SELECT location_id, AVG(book_amount) AS book_amount_location_avg 
        FROM booking 
        GROUP BY location_id
    ) AS la
        ON d.location_id = la.location_id
WHERE dt.booking_amount_destination_sum > da.book_amount_location_avg