android.database.sqlite.SQLiteDatabase.rawQuery() is not updating a column

Following is it's solution

public void set_datetime_next(Reminder r, String _newVal) {     
    String[] args = { new Integer(r.getID()).toString() };
    String query =
        "UPDATE " + DBConst.TABLE
      + " SET "   + DBConst.f_DATETIME_NEXT + "=" + _newVal
      + " WHERE " + DBConst.f_ID +"=?";
    Log.i(TAG, query);
    Cursor cu = db.rawQuery(query, args);
    cu.moveToFirst();
    cu.close();
}

While that makes sense, what really puzzles me is the requirement of calling moveToFirst() (or some other function which would "work with" the cursor in some way).
Without the call to both moveToFirst() and close(), the row was never updated. close() by itself, after the rawQuery(), did nothing