根据两个实例进行练习
1）创建库
mysql> create database Market;
Query OK, 1 row affected (0.00 sec)2）创建表
mysql> 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
-> );
Query OK, 0 rows affected (0.00 sec)3)字段插入（调换位置）
mysql> alter table customers MODIFY c_contact VARCHAR(50) after c_birth;
Query OK, 0 rows affected (0.05 sec)
Records: 0 Duplicates: 0 Warnings: 0
4)修改字段类型
mysql> alter table customers MODIFY c_name VARCHAR(70);
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
5)修改字段名
mysql> alter table customers CHANGE c_contact c_phone VARCHAR(50);
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
6)增加字段
mysql> alter table customers ADD c_gender CHAR(1);
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
7）修改表名（这一步做掉了，最后才添加上来。所以后面添加外键主表名依旧为customers。）
mysql> alter table customers RENAME customers_info;
Query OK, 0 rows affected (0.00 sec)
8)删除字段
mysql> alter table customers DROP c_city;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
9)修改存储引擎
mysql> alter table customers ENGINE=MyISAM;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
2、
（1）创建表、添加外键约束
mysql> create table orders (
-> o_num INT(11) PRIMARY KEY AUTO_INCREMENT,
-> o_date DATE,
-> c_id INT(11),
-> foreign key (c_id) references customers (c_num)
-> );
Query OK, 0 rows affected (0.01 sec)
（2）删除外键
先查看外键名
进行删除操作
mysql> alter table orders drop foreign key orders_ibfk_1;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0删除表
mysql> drop table customers;
Query OK, 0 rows affected (0.00 sec)
1）创建用户并授权
修改密码策略等级
mysql> set GLOBAL validate_password_policy='low';
Query OK, 0 rows affected (0.00 sec)
mysql> set global validate_password_length=0;
Query OK, 0 rows affected (0.00 sec)
创建用户
mysql> create user account1@localhost IDENTIFIED BY 'oldpwd1';
Query OK, 0 rows affected (0.00 sec)授权
mysql> grant SELECT,INSERT,UPDATE(info) on Team.player to account1@localhost;
Query OK, 0 rows affected (0.00 sec)
2）修改密码
mysql> alter user account1@localhost IDENTIFIED BY "newpwd2";
Query OK, 0 rows affected (0.00 sec)3）重新加载权限
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)4)查看权限
mysql> show grants for account1@localhost;
5）回收权限
mysql> revoke SELECT,INSERT,UPDATE(info) on Team.player from account1@localhost;
Query OK, 0 rows affected (0.00 sec)
