CREATE TABLE film_market_estimation (estimation_id DECIMAL, low_estimate DECIMAL, high_estimate DECIMAL, film_id DECIMAL, type TEXT, market_id DECIMAL, year DECIMAL)
CREATE TABLE market (market_id DECIMAL, country TEXT, number_cities DECIMAL)
CREATE TABLE film (film_id DECIMAL, title TEXT, studio TEXT, director TEXT, gross_in_dollar DECIMAL)

Return the average gross sales in dollars across all films.
SELECT AVG(gross_in_dollar) FROM film
SELECT AVG("gross_in_dollar") FROM "film"