mysql数据库字段内容互换

内容转自：

https://www.cnblogs.com/caicaizi/p/5557058.html

比如：

update tb_goods as a, tb_goods as b set a.goods_pay_number=b.goods_number ,a.goods_number=b.goods_pay_number where a.id=b.id and a.channel_id=7033 and a.app_id=21;