CREATE TABLE stadium (id NUMBER, name CLOB, home_games NUMBER, average_attendance NUMBER, total_attendance NUMBER, capacity_percentage NUMBER)
CREATE TABLE injury_accident (game_id NUMBER, id NUMBER, player CLOB, injury CLOB, number_of_matches CLOB, source CLOB)
CREATE TABLE game (stadium_id NUMBER, id NUMBER, season NUMBER, date CLOB, home_team CLOB, away_team CLOB, score CLOB, competition CLOB)

How many different kinds of information sources are there for injury accidents?
SELECT COUNT(DISTINCT source) FROM injury_accident
SELECT COUNT(DISTINCT "source") FROM "injury_accident"