public static ArrayList<Merchant> getAll(){
        
        SQLiteJDBC db = new SQLiteJDBC();
        ArrayList<Merchant> merchants = new ArrayList<Merchant>();
        
        String sql = "SELECT reg_num FROM merchants";
        ResultSet resultSet = db.query(sql);
        
        try {            
            while(resultSet.next()){
                Merchant merchant = new Merchant(resultSet.getInt("reg_num"));
                merchants.add(merchant);
            }
            db.close();
        }catch(Exception e) {
            System.err.println( e.getClass().getName() + ": " + e.getMessage() );
            System.exit(0);
        }
        
        return merchants;
    }