Android无法打开多个表的数据库

public class MyDatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "my_database.db";
    private static final int DATABASE_VERSION = 1;

    // 构造方法
    public MyDatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    // 创建数据库
    @Override
    public void onCreate(SQLiteDatabase db) {
        // 创建表1
        String createTable1 = "CREATE TABLE table1 (id INTEGER PRIMARY KEY, name TEXT)";
        db.execSQL(createTable1);

        // 创建表2
        String createTable2 = "CREATE TABLE table2 (id INTEGER PRIMARY KEY, age INTEGER)";
        db.execSQL(createTable2);
    }

    // 升级数据库
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 删除旧表
        db.execSQL("DROP TABLE IF EXISTS table1");
        db.execSQL("DROP TABLE IF EXISTS table2");

        // 创建新表
        onCreate(db);
    }
}

// 创建数据库对象
MyDatabaseHelper dbHelper = new MyDatabaseHelper(context);

// 获取可写的数据库对象
SQLiteDatabase db = dbHelper.getWritableDatabase();

// 执行SQL语句，操作表1
db.execSQL("INSERT INTO table1 (id, name) VALUES (1, 'John')");
db.execSQL("UPDATE table1 SET name = 'Tom' WHERE id = 1");
db.execSQL("DELETE FROM table1 WHERE id = 1");

// 执行SQL语句，操作表2
db.execSQL("INSERT INTO table2 (id, age) VALUES (1, 20)");
db.execSQL("UPDATE table2 SET age = 30 WHERE id = 1");
db.execSQL("DELETE FROM table2 WHERE id = 1");

// 关闭数据库连接
db.close();