CREATE TABLE flight (flno NUMBER, origin CLOB, destination CLOB, distance NUMBER, departure_date TIME, arrival_date TIME, price NUMBER, aid NUMBER)
CREATE TABLE certificate (eid NUMBER, aid NUMBER)
CREATE TABLE aircraft (aid NUMBER, name CLOB, distance NUMBER)
CREATE TABLE employee (eid NUMBER, name CLOB, salary NUMBER)

Which origin has most number of flights?
SELECT origin FROM flight GROUP BY origin ORDER BY COUNT(*) DESC LIMIT 1
SELECT "origin" FROM "flight" GROUP BY "origin" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY