Android SQLite Upgrade without losing data

changed it to:

db.execSQL("UPDATE new_quiz SET favourites = ( SELECT old_quiz.favourites FROM old_quiz WHERE new_quiz._id = old_quiz._id) WHERE EXISTS ( SELECT old_quiz.favourites FROM old_quiz WHERE new_quiz._id = old_quiz._id)");

Which works :D

public class DataHelper extends SQLiteOpenHelper {    private static final String dbName="dbName";     private Context context;    private  SQLiteDatabase db;    private final static int version = 1;    public  static final String SurveyTbl = "CREATE TABLE SurveyTbl (SurveyId TEXT PRIMARY KEY, Idref TEXT, SurveyDate TEXT)";    public DataHelper(Context context) {        super(context, dbName, null, version);        this.db = getWritableDatabase();        this.context = context;        Log.i("", "********************DatabaseHelper(Context context)");    }    @Override    public void onCreate(SQLiteDatabase db) {        try {        db.execSQL(SurveyTbl);        } catch (Exception e) {            Log.i("", "*******************onCreate");        }    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {        try {            db.execSQL("ALTER TABLE HandpumpSurveyTbl ADD COLUMN NalYozna TEXT");        } catch (Exception e) {            Log.i("", ""+e);        }         onCreate(db);    }}

I didn't get to see your Quiz table schema, but I assume it has fields like "question", "answer", "favorites", and some kind of a unique primary key to identify each question, which I will just call rowId for now.

// after renaming the old table and adding the new tabledb.execSQL("UPDATE new_quiz SET new_quiz.favorites = old_quiz.favorites where new_quiz.rowId = old_quiz.rowId");

That will update only the rows of the new quiz table that match the old quiz table, and set the favorites value from the old quiz table.

I assume you have some kind of a unique identifier to identify each question, so instead of the rowId above, you'll use that (question number or something).