Cursor cursor = sqliteDatabase.rawQuery("update "
+ DbMetaData.CART_TABLE_NAME + " set " + DbMetaData.PRODUCT_NUM
+ "=" + DbMetaData.PRODUCT_NUM + "+" + num + " where "
+ DbMetaData.ID + "=?", new String[]{id});
cursor.getCount() 总是返回 0;那么如何判断我更新成功呢?