public static void deleteQuiz(Quiz quiz) {
		// delete from quiz
		try {
			String statement = new String("DELETE FROM " + DBTable + " WHERE qid=?");
			PreparedStatement stmt = DBConnection.con.prepareStatement(statement);
			stmt.setInt(1, quiz.quizID);
			stmt.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		// delete from tag
		try {
			String statement = new String("DELETE FROM " + TagDBTable + " WHERE qid=?");
			PreparedStatement stmt = DBConnection.con.prepareStatement(statement);
			stmt.setInt(1, quiz.quizID);
			stmt.executeUpdate();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		QuizTakenRecord.deleteQuizTakenHistory(quiz);
		QuizCreatedRecord.deleteQuizCreatedHistory(quiz);		
	}