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

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"