mysql库/表练习

--创建Market数据库
create database Market;

--使用Market数据库
use Market;

--创建数据表customers
create table customers(
	c_num int(11)  primary key auto_increment,
	c_name varchar(50),
	c_contact varchar(50),
	c_city varchar(50),
	c_birth datetime not null
)

--将c_contact插入到c_birth后
alter table customers modify c_contact  varchar(50) after c_birth;

--将c_name的数据类型改为carchar(70)
alter table customers modify c_name varchar(70);

--将c_contact改名为c_phone
alter table customers change c_contact c_phone varchar(50);

--增加c_gender字段，数据类型为char(1)
alter table customers add e_gender char(1) after c_phone;

--将表名修改为customers_info
alter table customers rename customers_info;

--删除字段c_city
alter table customers_info drop c_city;

--修改数据表中的存储引擎为MyISAM
alter table customers_info engine=MyISAM;

--创建数据表orders
--因为外键约束是和表一起建的，所以在建表之前要先把上表的数据引擎改回系统默认的
alter table customers_info engine=InnoDB;

create table orders(
	o_num int(11) primary key auto_increment,
	o_date date,
	c_id varchar(50),
	constraint fk_orders foreign key(o_num) references customers_info(c_num)
);

--删除order表的外键约束，然后删除表customers
alter table orders drop foreign key fk_orders;
drop table customers;

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