public String getSingleEntry(String username) {
        Cursor cursor = db.query("credentials", null, " USERNAME=?", new String[] {username}, null, null, null);
        if (cursor.getCount() < 1) {
            cursor.close();
            return "NOT EXIST";
        }
        if(cursor.getColumnCount() <1 )
        {
            cursor.close();
            return "NOT EXIST";//apla to vala gia to message
            //Den pire ka8olou data an kai perase to Where Clause
        }
        cursor.moveToFirst();
        String password = cursor.getString(cursor.getColumnIndex("PASSWORD"));
        cursor.close();
        return password;
    }