CREATE TABLE people (people_id DECIMAL, district TEXT, name TEXT, party TEXT, age DECIMAL)
CREATE TABLE debate_people (debate_id DECIMAL, affirmative DECIMAL, negative DECIMAL, if_affirmative_win others)
CREATE TABLE debate (debate_id DECIMAL, date TEXT, venue TEXT, num_of_audience DECIMAL)

List the venues of debates in ascending order of the number of audience.
SELECT venue FROM debate ORDER BY num_of_audience
SELECT "venue" FROM "debate" ORDER BY "num_of_audience" NULLS FIRST