create database info;
show databases;
use info;
create table worker (
id int comment '序号',
sex char(1) comment '性别',
age int comment '年龄',
name varchar(10) comment '姓名',
id_card char(18) comment '身份证号',
worktime date comment '入职时间'
)comment '员工表';
DESC worker;
show tables;
alter table worker add guar varchar(10) comment'学历';
DESC worker;
show tables;
alter table worker modify id tinyint unsigned;
show tables;
alter table worker change sex gender varchar(1);
show tables;
alter table worker DROP guar;
show tables;
alter table worker RENAME to work_info;
DESC work_info;