数据库DDL练习，包含建表语句

# ddl练习相关sql代码，包含查看表结构，添加列，删除列，修改列数据类型，修改列名，删除列，修改编码，修改表名称

# ddl练习相关sql代码，包含查看表结构，添加列，删除列，修改列数据类型，修改列名，删除列，修改编码，修改表名称

create database my_2023_10_23;
use my_2023_10_23;
create table student (
   s_id int,
   s_name varchar(8),
   s_birth date,
   s_sex varchar(4)
);
insert into student values
(1,'赵雷','1990-01-01','男'),
(2,'钱电','1990-12-21','男'),
(3,'孙风','1990-05-20','男'),
(4,'李云','1990-08-06','男'),
(5,'周梅','1991-12-01','女'),
(6,'吴兰','1992-03-01','女'),
(7,'郑竹','1989-07-01','女'),
(8,'王菊','1990-01-20','女');

# 修改数据库编码
alter database my_2023_10_23 character set UTF8MB4;

# 查看表结构
DESC student;

# 添加列
alter table student add (s_class_name varchar(100));

# 修改列的数据类型
alter table student modify s_sex varchar(2);

# 修改列名
alter table student change s_sex s_gender char(1);

# 删除列
alter table student drop s_class_name;

# 修改表名称
alter table student rename to stu;

desc stu;
# 修改表名后就不存在了
desc student;