Android database manipulation approach.

I have a simple app which deals with database. All the database logic is done in a separate class, and in my MainActivity class I create an instance of the db class for querying the db.

Here my question is which is better approach?

1. Return a cursor object to the calling activity.

   public Cursor getAllData(){
   SQLiteDatabase database = helper.getWritableDatabase();
   String[] columns = {DB_Helper.UID,DB_Helper.FIRST_NAME,DB_Helper.LAST_NAME,DB_Helper.DOB};
   Cursor cursor = database.query(DB_Helper.TABLE_NAME,columns,null,null,null,null,null);     
   return cursor;
   }
   
   

2. Return a string after manipulating the cursor object.

   public String getAllData(){
   SQLiteDatabase database = helper.getWritableDatabase();
   String[] columns = {DB_Helper.UID,DB_Helper.FIRST_NAME,DB_Helper.LAST_NAME,DB_Helper.DOB};
   Cursor cursor = database.query(DB_Helper.TABLE_NAME,columns,null,null,null,null,null);
   StringBuffer stringBuffer = new StringBuffer();
   while (cursor.moveToNext()){
       int cid = cursor.getInt(cursor.getColumnIndex(DB_Helper.UID));
       String fname = cursor.getString(cursor.getColumnIndex(DB_Helper.FIRST_NAME));
       String lname = cursor.getString(cursor.getColumnIndex(DB_Helper.LAST_NAME));
       String dob = cursor.getString(cursor.getColumnIndex(DB_Helper.DOB));
       stringBuffer.append(cid +" "+ fname +" "+ lname +" "+ dob +"\n");
   }
   return stringBuffer.toString();
   }
   
   

3. Any other better approach?

I am complete beginner so please explain a little bit in support of you answer.