数据库更新不丢失数据

有一个包含 3 列的表格：id、title、poem、favorites。

因此，收藏夹写为 1 或 0，默认为 0，如果用户在收藏夹中添加一行，则更改。

问题是，如果我更新数据库（添加更多行），所有收藏夹将从用户中消失。如何在onUpgrade方法中将旧数据库中的收藏夹转移到新数据库中？

DbHelper 类代码

public class PoemsDbHelper extends SQLiteOpenHelper {
private static String DB_NAME = "brodsky.db";
private static String DB_PATH = "";
private static final int DB_VERSION = 3;

private SQLiteDatabase db;
private final Context context;
private boolean needUpdate = false;

public PoemsDbHelper(Context context) {
    super(context, DB_NAME, null, DB_VERSION);
    if (android.os.Build.VERSION.SDK_INT >= 17)
        DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
    else
        DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
    this.context = context;

    copyDataBase();

    this.getReadableDatabase();
}

public void updateDataBase() throws IOException {
    if (needUpdate) {
        File dbFile = new File(DB_PATH + DB_NAME);
        if (dbFile.exists())
            dbFile.delete();

        copyDataBase();

        needUpdate = false;
    }
}

private boolean checkDataBase() {
    File dbFile = new File(DB_PATH + DB_NAME);
    return dbFile.exists();
}

private void copyDataBase() {
    if (!checkDataBase()) {
        this.getReadableDatabase();
        this.close();
        try {
            copyDBFile();
        } catch (IOException mIOException) {
            throw new Error("ErrorCopyingDataBase");
        }
    }
}

private void copyDBFile() throws IOException {
    InputStream input = context.getAssets().open(DB_NAME);
    //InputStream input = context.getResources().openRawResource(R.raw.info);
    OutputStream output = new FileOutputStream(DB_PATH + DB_NAME);
    byte[] buffer = new byte[1024];
    int length;
    while ((length = input.read(buffer)) > 0)
        output.write(buffer, 0, length);
    output.flush();
    output.close();
    input.close();
}

public boolean openDataBase() throws SQLException {
    db = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.CREATE_IF_NECESSARY);
    return db != null;
}

@Override
public synchronized void close() {
    if (db != null)
       db.close();
    super.close();
}

@Override
public void onCreate(SQLiteDatabase db) {

}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    if (newVersion > oldVersion)
        needUpdate = true;
}

}