mysql直接create as select

create as select ：

create table grade_1 as
select *
from grade;

表结构比较：auto_increment变成了default '0'，所以用create as select 这种简单粗暴方式建表的时候一定要比较前后表结构。避免出现以下情况：

1、主键丢失

2、auto_increment -->default '0'

create table `grade_1`
(
    `gradeid`   int                               not null default '0' comment '年级id',
    `gradename` varchar(50) character set utf8mb3 not null comment '年级名称'
) engine = innodb
  default charset = utf8mb4
  collate = utf8mb4_0900_ai_ci;

create table `grade`
(
    `gradeid`   int(10)     not null auto_increment comment '年级id',
    `gradename` varchar(50) not null comment '年级名称',
    primary key (`gradeid`)
) engine = innodb
  default charset = utf8