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: 0mysql> 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)
