# 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;