数据库基本语法：
DDL：Data Defination Lanuage: 数据定义语言CREATE, ALTER, DROP
DML：Data Manapulate Language: 数据操作语言INSERT, REPLACE, UPDATE, DELETE
DCL：Data Control Language: 数据控制语言GRANT, REVOKE
常用命令：
mysql命令不区分大小写 这些是基本常识
DDL CREATEALTERDROP
DML 操纵语言INSERTUPDATEDELETE
DCL 控制语言GRANTREVOKE
第一篇 DDL 库和表 create alter drop
mysql> create database mydb;
Query OK, 1 row affected (0.01 sec)
mysql> use mydb;
Database changed
mysql> show tables;
Empty set (0.00 sec)
mysql> create table students (id char(20),name char(20),age char(10),score char(10)); 建表并添加4个字段和字段的类型
Query OK, 0 rows affected (0.10 sec)
mysql> show tables;
+----------------+
| Tables_in_mydb |
+----------------+
| students       |
+----------------+
1 row in set (0.00 sec)
mysql> create table teachers as select * from students; 建立教师表，字段同学生表
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> show tables;
+----------------+
| Tables_in_mydb |
+----------------+
| students       |
| teachers       |
+----------------+
2 rows in set (0.00 sec)
mysql> desc students;
mysql> desc teachers;
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id    | char(20) | YES  |     | NULL    |       |
| name  | char(20) | YES  |     | NULL    |       |
| age   | char(10) | YES  |     | NULL    |       |
| score | char(10) | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+
mysql> alter table teachers add subject varchar(100); 添加字段
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> desc teachers;
+---------+--------------+------+-----+---------+-------+
| Field   | Type         | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| id      | char(20)     | YES  |     | NULL    |       |
| name    | char(20)     | YES  |     | NULL    |       |
| age     | char(10)     | YES  |     | NULL    |       |
| score   | char(10)     | YES  |     | NULL    |       |
| subject | varchar(100) | YES  |     | NULL    |       |
+---------+--------------+------+-----+---------+-------+
mysql> alter table teachers drop score; 删除字段
Query OK, 0 rows affected (0.05 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> desc teachers;
+---------+--------------+------+-----+---------+-------+
| Field   | Type         | Null | Key | Default | Extra |
+---------+--------------+------+-----+---------+-------+
| id      | char(20)     | YES  |     | NULL    |       |
| name    | char(20)     | YES  |     | NULL    |       |
| age     | char(10)     | YES  |     | NULL    |       |
| subject | varchar(100) | YES  |     | NULL    |       |
+---------+--------------+------+-----+---------+-------+
mysql> alter table teachers change id teacherid char(30); 修改字段名，用change
Query OK, 0 rows affected (0.06 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> desc teachers;
+-----------+--------------+------+-----+---------+-------+
| Field     | Type         | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+-------+
| teacherid | char(30)     | YES  |     | NULL    |       |
| name      | char(20)     | YES  |     | NULL    |       |
| age       | char(10)     | YES  |     | NULL    |       |
| subject   | varchar(100) | YES  |     | NULL    |       |
+-----------+--------------+------+-----+---------+-------+
mysql> alter table teachers modify teacherid varchar(5); 修改字段属性，用modify
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0
mysql> desc teachers;
+-----------+--------------+------+-----+---------+-------+
| Field     | Type         | Null | Key | Default | Extra |
+-----------+--------------+------+-----+---------+-------+
| teacherid | varchar(5)   | YES  |     | NULL    |       |
| name      | char(20)     | YES  |     | NULL    |       |
| age       | char(10)     | YES  |     | NULL    |       |
| subject   | varchar(100) | YES  |     | NULL    |       |
+-----------+--------------+------+-----+---------+-------+
mysql> drop table teachers; 删除表，drop table table_name
Query OK, 0 rows affected (0.00 sec)
总结1：查看库中的表：SHOW TABLES FROM db_name；查看表的结构：DESC tb_name;删除表：DROP TABLE tb_name；
修改表：ALTER TABLE tb_nameMODIFY 改字段属性CHANGE 改字段名称ADD 添加字段DROP 删除字段
help create table获取帮助 help alter table
第二篇 DML 数据修改 insert update delete ; select
mysql> insert into students (id,name,age,score) value('1','wxtan','18','99'),('2','yull','17','80');  增加表内数据，insert into
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0
mysql> select * from students;
+------+-------+------+-------+
| id   | name  | age  | score |
+------+-------+------+-------+
| 1    | wxtan | 18   | 99    |
| 2    | yull  | 17   | 80    |
+------+-------+------+-------+
mysql> insert into students value('3','AA','30','60');  （如果全部字段都添加可以不用写）
Query OK, 1 row affected (0.00 sec)
mysql> select * from students;
+------+-------+------+-------+
| id   | name  | age  | score |
+------+-------+------+-------+
| 1    | wxtan | 18   | 99    |
| 2    | yull  | 17   | 80    |
| 3    | AA    | 30   | 60    |
+------+-------+------+-------+
mysql> update students set age=14 where id=1; 修改表内数据，update table_name
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql> select * from students;
+------+-------+------+-------+
| id   | name  | age  | score |
+------+-------+------+-------+
| 1    | wxtan | 14   | 99    |
| 2    | yull  | 17   | 80    |
| 3    | AA    | 30   | 60    |
+------+-------+------+-------+
3 rows in set (0.00 sec)
mysql> update students set age='28' where name='yull'; 修改表内数据，update table_name
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
mysql> select * from students;
+------+-------+------+-------+
| id   | name  | age  | score |
+------+-------+------+-------+
| 1    | wxtan | 14   | 99    |
| 2    | yull  | 28   | 80    |
| 3    | AA    | 30   | 60    |
+------+-------+------+-------+
3 rows in set (0.00 sec)
mysql> select * from students;
+------+-------+------+-------+
| id   | name  | age  | score |
+------+-------+------+-------+
| 1    | wxtan | 14   | 99    |
| 2    | yull  | 28   | 80    |
| 5    | bb    | 44   | 55    |
| 6    | cc    | 44   | 60    |
+------+-------+------+-------+
4 rows in set (0.00 sec)
mysql> delete from students where age='44'; 删除表内数据，delete from
Query OK, 2 rows affected (0.00 sec)
mysql> select * from students;
+------+-------+------+-------+
| id   | name  | age  | score |
+------+-------+------+-------+
| 1    | wxtan | 14   | 99    |
| 2    | yull  | 28   | 80    |
+------+-------+------+-------+
mysql> delete from students where age='14' or score='80'; 可以用or and等条件表达式
Query OK, 2 rows affected (0.00 sec)
mysql> select * from students;
Empty set (0.00 sec)
mysql> select * from students; 数据查询，select from
+------+--------+------+-------+
| id   | name   | age  | score |
+------+--------+------+-------+
| 1    | apple  | 20   | 88    |
| 3    | xigua  | 10   | 50    |
| 2    | banana | 30   | 68    |
+------+--------+------+-------+
3 rows in set (0.00 sec)
mysql> select id,name from students;
+------+--------+
| id   | name   |
+------+--------+
| 1    | apple  |
| 3    | xigua  |
| 2    | banana |
+------+--------+
3 rows in set (0.00 sec)
mysql> select id,name from students where age=20;
+------+-------+
| id   | name  |
+------+-------+
| 1    | apple |
+------+-------+
1 row in set (0.00 sec)
第三篇 DCL 权限 grant revoke；show grants for
mysql> grant select,insert,update on mydb.students to 'wxtan2'@'192.168.8.%' identified by '123'; 给权限到某表，授予某账户（账户不存在则创建）
mysql> flush privileges; 刷新权限
[root@test mysql]# mysql -uwxtan2 -p123 -h192.168.8.104 从192.168.8.%进入数据库
Welcome to the MariaDB monitor.
MySQL [mydb]> select * from students;
+------+--------+------+-------+
| id   | name   | age  | score |
+------+--------+------+-------+
| 1    | apple  | 20   | 88    |
| 3    | xigua  | 10   | 50    |
| 2    | banana | 30   | 68    |
+------+--------+------+-------+
3 rows in set (0.00 sec)
MySQL [mydb]> insert into students value('4','guapi','40','50'); 有insert权限
Query OK, 1 row affected (0.02 sec)
MySQL [mydb]> update students set name='apple222' where id='1'; 有update权限
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
MySQL [mydb]> select * from students;
+------+----------+------+-------+
| id   | name     | age  | score |
+------+----------+------+-------+
| 1    | apple222 | 20   | 88    |
| 3    | xigua    | 10   | 50    |
| 2    | banana   | 30   | 68    |
| 4    | guapi    | 40   | 50    |
+------+----------+------+-------+
4 rows in set (0.00 sec)
MySQL [mydb]> delete from students where name='banana'; 没有delete权限
ERROR 1142 (42000): DELETE command denied to user 'wxtan2'@'192.168.8.101' for table 'students'
mysql> revoke update on mydb.students from 'wxtan2'@'192.168.8.%'; 回收update权限
mysql> flush privileges;
MySQL [mydb]> update students set name='apple545' where id='1'; 发现无法执行update命令
ERROR 1142 (42000): UPDATE command denied to user 'wxtan2'@'192.168.8.101' for table 'students'
MySQL [mydb]> insert into students value('6','guapi','40','50'); insert命令不受影响
Query OK, 1 row affected (0.00 sec)
MySQL [mydb]> select * from students; select命令不受影响
+------+----------+------+-------+
| id   | name     | age  | score |
+------+----------+------+-------+
| 1    | apple555 | 20   | 88    |
| 3    | xigua    | 10   | 50    |
| 2    | banana   | 30   | 68    |
| 4    | guapi    | 40   | 50    |
| 6    | guapi    | 40   | 50    |
+------+----------+------+-------+
mysql> show grants for 'wxtan2'@'192.168.8.%'; 查询用户的权限命令；usage表示只有使用权
+-----------------------------------------------------------------------------------------------------------------+
| Grants for wxtan2@192.168.8.%                                                                                   |
+-----------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'wxtan2'@'192.168.8.%' IDENTIFIED BY PASSWORD '*23AE809DDACAF96AF0FD78ED04B6A265E05AA257' |
| GRANT SELECT, INSERT ON `mydb`.`students` TO 'wxtan2'@'192.168.8.%'                                             |
+-----------------------------------------------------------------------------------------------------------------+
mysql> grant all privileges on mydb.students to 'wxtan2'@'192.168.8.%' identified by '123456'; 给所有权限，并修改密码
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
第四篇 修改数据库默认密码
/etc/init.d/mysql stop   (service mysqld stop )
/usr/bin/mysqld_safe --skip-grant-tables
另外开个SSH连接
[root@localhost ~]# mysql
mysql>use mysql;
mysql>update user set password=password("123456") where user="root";
mysql>flush privileges;
mysql>exit
CTRL+Z 终止进程
[root@apple ~]# jobs
[1]+  Stopped                 mysqld_safe --skip-grant-tables
[root@apple ~]# kill %1
[root@apple ~]# service mysqld start
Starting MySQL SUCCESS!
方法1： 用SET PASSWORD命令
首先登录MySQL。
格式：mysql> set password for 用户名@localhost = password('新密码');
例子：mysql> set password for root@localhost = password('123');
方法2：用mysqladmin
格式：mysqladmin -u用户名 -p旧密码 password 新密码
例子：mysqladmin -uroot -p123456 password 123
方法3：用UPDATE直接编辑user表
首先登录MySQL。
mysql> use mysql;
mysql> update user set password=password('123') where user='root' and host='localhost';
mysql> flush privileges;
方法4：在忘记root密码的时候，可以这样
以windows为例：
1. 关闭正在运行的MySQL服务。
2. 打开DOS窗口，转到mysql\bin目录。
3. 输入mysqld --skip-grant-tables 回车。--skip-grant-tables 的意思是启动MySQL服务的时候跳过权限表认证。
4. 再开一个DOS窗口（因为刚才那个DOS窗口已经不能动了），转到mysql\bin目录。
5. 输入mysql回车，如果成功，将出现MySQL提示符 >。
6. 连接权限数据库： use mysql; 。
6. 改密码：update user set password=password("123") where user="root";（别忘了最后加分号） 。
7. 刷新权限（必须步骤）：flush privileges;　。
8. 退出 quit。
9. 注销系统，再进入，使用用户名root和刚才设置的新密码123登录。