一、库的建立

mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | mydb2_stuinfo      | | mydb3_employee     | | mydb4_product      | | mydbl_test         | | mysql              | | performance_schema | | sys                | | temp2              | +--------------------+ 9 rows in set (0.00 sec)  mysql> create database mydb6_product; Query OK, 1 row affected (0.01 sec)  mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | mydb2_stuinfo      | | mydb3_employee     | | mydb4_product      | | mydb6_product      | | mydbl_test         | | mysql              | | performance_schema | | sys                | | temp2              | +--------------------+ 10 rows in set (0.00 sec)

二、建立employees表  （有主键，非空，默认值的要求）

mysql> create table employees(     -> id int primary key,     -> name varchar(50) not null,     -> age int,     -> gender varchar(10) not null default 'unknown',     -> salary float); Query OK, 0 rows affected (0.03 sec)  mysql> desc employees; +--------+-------------+------+-----+---------+-------+ | Field  | Type        | Null | Key | Default | Extra | +--------+-------------+------+-----+---------+-------+ | id     | int         | NO   | PRI | NULL    |       | | name   | varchar(50) | NO   |     | NULL    |       | | age    | int         | YES  |     | NULL    |       | | gender | varchar(10) | NO   |     | unknown |       | | salary | float       | YES  |     | NULL    |       | +--------+-------------+------+-----+---------+-------+ 5 rows in set (0.00 sec)

三、建立 orders表 （有主键和非空的要求）

​ mysql> create table orders(     -> id int primary key,     -> name varchar(100) not null,     -> price float,     -> quantity int,     -> category varchar(50)); Query OK, 0 rows affected (0.03 sec)  mysql> desc orders; +----------+--------------+------+-----+---------+-------+ | Field    | Type         | Null | Key | Default | Extra | +----------+--------------+------+-----+---------+-------+ | id       | int          | NO   | PRI | NULL    |       | | name     | varchar(100) | NO   |     | NULL    |       | | price    | float        | YES  |     | NULL    |       | | quantity | int          | YES  |     | NULL    |       | | category | varchar(50)  | YES  |     | NULL    |       | +----------+--------------+------+-----+---------+-------+ 5 rows in set (0.00 sec)  ​

四、建立invoices表 （有主键自增长，外键关联，数值范围的要求）

mysql> create table invoices(     -> number int primary key,     -> order_id int,foreign key (order_id) references orders(id),     -> in_date date,     -> total_amount float ,check(total_amount>0)); Query OK, 0 rows affected (0.04 sec)  mysql> alter table invoices modify number int auto_increment; Query OK, 0 rows affected (0.06 sec) Records: 0  Duplicates: 0  Warnings: 0  mysql> desc invoices; +--------------+-------+------+-----+---------+----------------+ | Field        | Type  | Null | Key | Default | Extra          | +--------------+-------+------+-----+---------+----------------+ | number       | int   | NO   | PRI | NULL    | auto_increment | | order_id     | int   | YES  | MUL | NULL    |                | | in_date      | date  | YES  |     | NULL    |                | | total_amount | float | YES  |     | NULL    |                | +--------------+-------+------+-----+---------+----------------+ 4 rows in set (0.00 sec)