mysql 如何给大表添加字段

create table xx_order_bak like xx_order; alter table xx_order_bak add column `unit` int(10) DEFAULT 1; INSERT INTO xx_order_bak(`id`, `create_date`, `modify_date`, `address`, `amount_paid`) select * from xx_order; rename table xx_order to xx_order_bak1; <p>rename table xx_order_bak to xx_order;</p>