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第三章：数据库查询.md | 975 +++++++++++++++++++++
第二章：数据库管理及数据类型.md | 861 +++++++++++++++++++
第五章：权限管理及数据备份与恢复.md | 1228 +++++++++++++++++++++++++++
第四章：数据库日志管理.md | 135 +++
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create mode 100644 第三章：数据库查询.md
create mode 100644 第二章：数据库管理及数据类型.md
create mode 100644 第五章：权限管理及数据备份与恢复.md
create mode 100644 第四章：数据库日志管理.md
diff --git a/第三章：数据库查询.md b/第三章：数据库查询.md
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+数据库查询
+
+
+
+------
+
+## 一：基本查询
+
+#### 1.简介
+
+ 单表查询
+
+ 简单查询
+
+ 通过条件查询
+
+ 查询排序
+
+ 限制查询记录数
+
+ 使用集合函数查询
+
+ 分组查询
+
+ 使用正则表达式查询
+
+#### 2.案例
+
+创建案例所需表：company.employee5
+
+```shell
+ 雇员编号 id int
+ 雇员姓名 name varchar(30)
+ 雇员性别 sex enum
+ 雇用时期 hire_date date
+ 职位 post varchar(50)
+ 职位描述 job_description varchar(100)
+ 薪水 salary double(15,2)
+ 办公室 office int
+ 部门编号 dep_id int
+```
+
+```shell
+MySQL [(none)]> CREATE TABLE company.employee5(
+ id int primary key AUTO_INCREMENT not null,
+ name varchar(30) not null,
+ sex enum('male','female') default 'male' not null,
+ hire_date date not null,
+ post varchar(50) not null,
+ job_description varchar(100),
+ salary double(15,2) not null,
+ office int,
+ dep_id int
+ );
+```
+
+插入模拟数据：
+
+```shell
+MySQL [(none)]> insert into company.employee5(name,sex,hire_date,post,job_description,salary,office,dep_id) values
+ ('jack','male','20180202','instructor','teach',5000,501,100),
+ ('tom','male','20180203','instructor','teach',5500,501,100),
+ ('robin','male','20180202','instructor','teach',8000,501,100),
+ ('alice','female','20180202','instructor','teach',7200,501,100),
+ ('','male','20180202','hr','hrcc',600,502,101),
+ ('harry','male','20180202','hr',NULL,6000,502,101),
+ ('emma','female','20180206','sale','salecc',20000,503,102),
+ ('christine','female','20180205','sale','salecc',2200,503,102),
+ ('zhuzhu','male','20180205','sale',NULL,2200,503,102),
+ ('gougou','male','20180205','sale','',2200,503,102);
+```
+
+语法格式：
+
+ select 字段名称,字段名称2...... from 表名 [条件]
+
+##### a.简单查询
+
+```shell
+MySQL [company]> select * from employee5;
++----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
+| 1 | jack | male | 2018-02-02 | instructor | teach | 5000.00 | 501 | 100 |
+| 2 | tom | male | 2018-02-03 | instructor | teach | 5500.00 | 501 | 100 |
+| 3 | robin | male | 2018-02-02 | instructor | teach | 8000.00 | 501 | 100 |
+| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
+| 5 | | male | 2018-02-02 | hr | hrcc | 600.00 | 502 | 101 |
+| 6 | harry | male | 2018-02-02 | hr | NULL | 6000.00 | 502 | 101 |
+| 7 | emma | female | 2018-02-06 | sale | salecc | 20000.00 | 503 | 102 |
+| 8 | christine | female | 2018-02-05 | sale | salecc | 2200.00 | 503 | 102 |
+| 9 | zhuzhu | male | 2018-02-05 | sale | NULL | 2200.00 | 503 | 102 |
+| 10 | gougou | male | 2018-02-05 | sale | | 2200.00 | 503 | 102 |
++----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
+10 rows in set (0.00 sec)
+
+MySQL [company]> select name, salary, dep_id from employee5 where id <=5;
++-------+---------+--------+
+| name | salary | dep_id |
++-------+---------+--------+
+| jack | 5000.00 | 100 |
+| tom | 5500.00 | 100 |
+| robin | 8000.00 | 100 |
+| alice | 7200.00 | 100 |
+| | 600.00 | 101 |
++-------+---------+--------+
+5 rows in set (0.00 sec)
+```
+
+##### b.避免重复
+
+ 不能部分使用DISTINCT，通常仅用于某一字段
+
+```shell
+MySQL [company]> SELECT post FROM employee5;
++------------+
+| post |
++------------+
+| instructor |
+| instructor |
+| instructor |
+| instructor |
+| hr |
+| hr |
+| sale |
+| sale |
+| sale |
+| sale |
++------------+
+10 rows in set (0.00 sec)
+
+MySQL [company]> SELECT distinct post FROM employee5;
++------------+
+| post |
++------------+
+| instructor |
+| hr |
+| sale |
++------------+
+3 rows in set (0.00 sec)
+```
+
+##### c.四则运算查询
+
+```shell
+MySQL [company]> SELECT name, salary, salary*14 FROM employee5;
++-----------+----------+-----------+
+| name | salary | salary*14 |
++-----------+----------+-----------+
+| jack | 5000.00 | 70000.00 |
+| tom | 5500.00 | 77000.00 |
+| robin | 8000.00 | 112000.00 |
+| alice | 7200.00 | 100800.00 |
+| | 600.00 | 8400.00 |
+| harry | 6000.00 | 84000.00 |
+| emma | 20000.00 | 280000.00 |
+| christine | 2200.00 | 30800.00 |
+| zhuzhu | 2200.00 | 30800.00 |
+| gougou | 2200.00 | 30800.00 |
++-----------+----------+-----------+
+10 rows in set (0.01 sec)
+
+MySQL [company]> SELECT name, salary, salary*14 AS Annual_salary FROM employee5;
++-----------+----------+---------------+
+| name | salary | Annual_salary |
++-----------+----------+---------------+
+| jack | 5000.00 | 70000.00 |
+| tom | 5500.00 | 77000.00 |
+| robin | 8000.00 | 112000.00 |
+| alice | 7200.00 | 100800.00 |
+| | 600.00 | 8400.00 |
+| harry | 6000.00 | 84000.00 |
+| emma | 20000.00 | 280000.00 |
+| christine | 2200.00 | 30800.00 |
+| zhuzhu | 2200.00 | 30800.00 |
+| gougou | 2200.00 | 30800.00 |
++-----------+----------+---------------+
+10 rows in set (0.00 sec)
+
+MySQL [company]> SELECT name, salary, salary*14 Annual_salary FROM employee5;
++-----------+----------+---------------+
+| name | salary | Annual_salary |
++-----------+----------+---------------+
+| jack | 5000.00 | 70000.00 |
+| tom | 5500.00 | 77000.00 |
+| robin | 8000.00 | 112000.00 |
+| alice | 7200.00 | 100800.00 |
+| | 600.00 | 8400.00 |
+| harry | 6000.00 | 84000.00 |
+| emma | 20000.00 | 280000.00 |
+| christine | 2200.00 | 30800.00 |
+| zhuzhu | 2200.00 | 30800.00 |
+| gougou | 2200.00 | 30800.00 |
++-----------+----------+---------------+
+10 rows in set (0.00 sec)
+```
+
+##### d.定义显示格式
+
+ CONCAT() 函数用于连接字符串
+
+```shell
+MySQL [company]> SELECT concat(name, 's annual salary: ', salary*14) AS Annual_salary FROM employee5;
++------------------------------------+
+| Annual_salary |
++------------------------------------+
+| jacks annual salary: 70000.00 |
+| toms annual salary: 77000.00 |
+| robins annual salary: 112000.00 |
+| alices annual salary: 100800.00 |
+| s annual salary: 8400.00 |
+| harrys annual salary: 84000.00 |
+| emmas annual salary: 280000.00 |
+| christines annual salary: 30800.00 |
+| zhuzhus annual salary: 30800.00 |
+| gougous annual salary: 30800.00 |
++------------------------------------+
+10 rows in set (0.00 sec)
+```
+
+##### e.单条件查询
+
+```shell
+MySQL [company]> SELECT name,post FROM employee5 WHERE post='hr';
++-------+------+
+| name | post |
++-------+------+
+| | hr |
+| harry | hr |
++-------+------+
+2 rows in set (0.00 sec)
+```
+
+##### f.多条件查询
+
+```shell
+MySQL [company]> SELECT name,salary FROM employee5 WHERE post='hr' AND salary>10000;
+Empty set (0.00 sec)
+
+MySQL [company]> select * from employee5 where salary>5000 and salary<10000 or dep_id=102;
++----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
+| 2 | tom | male | 2018-02-03 | instructor | teach | 5500.00 | 501 | 100 |
+| 3 | robin | male | 2018-02-02 | instructor | teach | 8000.00 | 501 | 100 |
+| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
+| 6 | harry | male | 2018-02-02 | hr | NULL | 6000.00 | 502 | 101 |
+| 7 | emma | female | 2018-02-06 | sale | salecc | 20000.00 | 503 | 102 |
+| 8 | christine | female | 2018-02-05 | sale | salecc | 2200.00 | 503 | 102 |
+| 9 | zhuzhu | male | 2018-02-05 | sale | NULL | 2200.00 | 503 | 102 |
+| 10 | gougou | male | 2018-02-05 | sale | | 2200.00 | 503 | 102 |
++----+-----------+--------+------------+------------+-----------------+----------+--------+--------+
+8 rows in set (0.00 sec)
+```
+
+##### g.关键字
+
+ BETWEEN AND
+
+```shell
+MySQL [company]> SELECT name,salary FROM employee5 WHERE salary BETWEEN 5000 AND 15000;
++-------+---------+
+| name | salary |
++-------+---------+
+| jack | 5000.00 |
+| tom | 5500.00 |
+| robin | 8000.00 |
+| alice | 7200.00 |
+| harry | 6000.00 |
++-------+---------+
+5 rows in set (0.00 sec)
+
+MySQL [company]> SELECT name,salary FROM employee5 WHERE salary NOT BETWEEN 5000 AND 15000;
++-----------+----------+
+| name | salary |
++-----------+----------+
+| | 600.00 |
+| emma | 20000.00 |
+| christine | 2200.00 |
+| zhuzhu | 2200.00 |
+| gougou | 2200.00 |
++-----------+----------+
+5 rows in set (0.00 sec)
+```
+
+ IS NULL
+
+```shell
+MySQL [company]> SELECT name,job_description FROM employee5 WHERE job_description IS NULL;
++--------+-----------------+
+| name | job_description |
++--------+-----------------+
+| harry | NULL |
+| zhuzhu | NULL |
++--------+-----------------+
+2 rows in set (0.00 sec)
+
+MySQL [company]> SELECT name,job_description FROM employee5 WHERE job_description IS NOT NULL;
++-----------+-----------------+
+| name | job_description |
++-----------+-----------------+
+| jack | teach |
+| tom | teach |
+| robin | teach |
+| alice | teach |
+| | hrcc |
+| emma | salecc |
+| christine | salecc |
+| gougou | |
++-----------+-----------------+
+8 rows in set (0.00 sec)
+
+MySQL [company]> SELECT name,job_description FROM employee5 WHERE job_description='';
++--------+-----------------+
+| name | job_description |
++--------+-----------------+
+| gougou | |
++--------+-----------------+
+1 row in set (0.00 sec)
+```
+
+注意：（NULL说明）
+
+ 等价于没有任何值、是未知数
+
+ NULL与0、空字符串、空格都不同,NULL没有分配存储空间
+
+ 对空值做加、减、乘、除等运算操作，结果仍为空
+
+ 比较时使用关键字用“is null”和“is not null”
+
+ 排序时比其他数据都小（索引默认是降序排列，小→大），所以NULL值总是排在最前
+
+IN集合查询
+
+```shell
+MySQL [company]> SELECT name, salary FROM employee5 WHERE salary=4000 OR salary=5000 OR salary=6000 OR salary=9000 ;
++-------+---------+
+| name | salary |
++-------+---------+
+| jack | 5000.00 |
+| harry | 6000.00 |
++-------+---------+
+2 rows in set (0.00 sec)
+
+MySQL [company]> SELECT name, salary FROM employee5 WHERE salary IN (4000,5000,6000,9000) ;
++-------+---------+
+| name | salary |
++-------+---------+
+| jack | 5000.00 |
+| harry | 6000.00 |
++-------+---------+
+2 rows in set (0.00 sec)
+
+MySQL [company]> SELECT name, salary FROM employee5 WHERE salary NOT IN (4000,5000,6000,9000) ;
++-----------+----------+
+| name | salary |
++-----------+----------+
+| tom | 5500.00 |
+| robin | 8000.00 |
+| alice | 7200.00 |
+| | 600.00 |
+| emma | 20000.00 |
+| christine | 2200.00 |
+| zhuzhu | 2200.00 |
+| gougou | 2200.00 |
++-----------+----------+
+8 rows in set (0.01 sec)
+```
+
+##### h.模糊查询
+
+ 关键字LIKE
+
+ 通配符%：所有字符
+
+ 通配符_： 一个字符
+
+```shell
+MySQL [company]> SELECT * FROM employee5 WHERE name LIKE 'al%';
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+1 row in set (0.00 sec)
+
+MySQL [company]> SELECT * FROM employee5 WHERE name LIKE 'al___';
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+1 row in set (0.00 sec)
+```
+
+##### i.排序查询
+
+```shell
+MySQL [company]> select name,salary from employee5 order by salary;
++-----------+----------+
+| name | salary |
++-----------+----------+
+| | 600.00 |
+| christine | 2200.00 |
+| zhuzhu | 2200.00 |
+| gougou | 2200.00 |
+| jack | 5000.00 |
+| tom | 5500.00 |
+| harry | 6000.00 |
+| alice | 7200.00 |
+| robin | 8000.00 |
+| emma | 20000.00 |
++-----------+----------+
+10 rows in set (0.01 sec)
+
+MySQL [company]> select name,salary from employee5 order by salary desc;
++-----------+----------+
+| name | salary |
++-----------+----------+
+| emma | 20000.00 |
+| robin | 8000.00 |
+| alice | 7200.00 |
+| harry | 6000.00 |
+| tom | 5500.00 |
+| jack | 5000.00 |
+| christine | 2200.00 |
+| zhuzhu | 2200.00 |
+| gougou | 2200.00 |
+| | 600.00 |
++-----------+----------+
+
+MySQL [company]> select name,salary from employee5 order by salary desc limit 3; //控制显示前3行
++-------+----------+
+| name | salary |
++-------+----------+
+| emma | 20000.00 |
+| robin | 8000.00 |
+| alice | 7200.00 |
++-------+----------+
+3 rows in set (0.00 sec)
+
+MySQL [company]> select name,salary from employee5 order by salary desc limit 1,3; //从序号1开始显示三行的内容
++-------+---------+
+| name | salary |
++-------+---------+
+| robin | 8000.00 |
+| alice | 7200.00 |
+| harry | 6000.00 |
++-------+---------+
+3 rows in set (0.00 sec)
+```
+
+注意：
+
+ ascending 美音 /ə'sɛndɪŋ/ 升序
+
+ descending 美音 /dɪ'sɛndɪŋ/ 降序
+
+##### j.集合函数查询
+
+ count：可以查看共有多少条记录
+
+```shell
+MySQL [company]> select count(*) from employee5;
++----------+
+| count(*) |
++----------+
+| 10 |
++----------+
+1 row in set (0.00 sec)
+
+MySQL [company]> select count(name) from employee5;
++-------------+
+| count(name) |
++-------------+
+| 10 |
++-------------+
+1 row in set (0.00 sec)
+
+```
+
+ max：查看最大值
+
+```shell
+MySQL [company]> select max(salary) from employee5;
++-------------+
+| max(salary) |
++-------------+
+| 20000.00 |
++-------------+
+1 row in set (0.00 sec)
+```
+
+ min：查看最小值
+
+```shell
+MySQL [company]> select min(salary) from employee5;
++-------------+
+| min(salary) |
++-------------+
+| 600.00 |
++-------------+
+1 row in set (0.00 sec)
+```
+
+ avg：查看平均值
+
+```shell
+MySQL [company]> select avg(salary) from employee5;
++-------------+
+| avg(salary) |
++-------------+
+| 5890.000000 |
++-------------+
+1 row in set (0.00 sec)
+```
+
+ sum：求和
+
+ sale这个部门的总工资
+
+```shell
+MySQL [company]> select concat("Total Department Wages：",sum(salary)) from employee5 where post='sale';
++-------------------------------------------------+
+| concat("Total Department Wages：",sum(salary)) |
++-------------------------------------------------+
+| Total Department Wages：26600.00 |
++-------------------------------------------------+
+1 row in set (0.00 sec)
+```
+
+ 获取薪水最高的这个人的详细信息
+
+```shell
+MySQL [company]> select * from employee5 where salary = (select max(salary) from employee5);
++----+------+--------+------------+------+-----------------+----------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+------+--------+------------+------+-----------------+----------+--------+--------+
+| 7 | emma | female | 2018-02-06 | sale | salecc | 20000.00 | 503 | 102 |
++----+------+--------+------------+------+-----------------+----------+--------+--------+
+1 row in set (0.00 sec)
+```
+
+##### k.分组查询
+
+ GROUP BY和GROUP_CONCAT()函数一起使用
+
+ 获取部门ID相同的员工并把名字拼接到一起
+
+```shell
+MySQL [company]> SELECT dep_id,GROUP_CONCAT(name) FROM employee5 GROUP BY dep_id;
++--------+------------------------------+
+| dep_id | GROUP_CONCAT(name) |
++--------+------------------------------+
+| 100 | jack,tom,robin,alice |
+| 101 | ,harry |
+| 102 | emma,christine,zhuzhu,gougou |
++--------+------------------------------+
+3 rows in set (0.01 sec)
+```
+
+ GROUP BY和集合函数一起使用
+
+ 获取部门最高薪资
+
+```shell
+MySQL [company]> SELECT post,max(salary) FROM employee5 GROUP BY post;
++------------+-------------+
+| post | max(salary) |
++------------+-------------+
+| hr | 6000.00 |
+| instructor | 8000.00 |
+| sale | 20000.00 |
++------------+-------------+
+3 rows in set (0.00 sec)
+```
+
+##### l.正则查询
+
+```shell
+以什么开头
+MySQL [company]> SELECT * FROM employee5 WHERE name REGEXP '^ali';
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+1 row in set (0.00 sec)
+
+以什么结尾
+MySQL [company]> SELECT * FROM employee5 WHERE name REGEXP 'ce$';
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+| 4 | alice | female | 2018-02-02 | instructor | teach | 7200.00 | 501 | 100 |
++----+-------+--------+------------+------------+-----------------+---------+--------+--------+
+1 row in set (0.01 sec)
+
+连续出现n次
+MySQL [company]> SELECT * FROM employee5 WHERE name REGEXP 'm{2}';
++----+------+--------+------------+------+-----------------+----------+--------+--------+
+| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
++----+------+--------+------------+------+-----------------+----------+--------+--------+
+| 7 | emma | female | 2018-02-06 | sale | salecc | 20000.00 | 503 | 102 |
++----+------+--------+------------+------+-----------------+----------+--------+--------+
+1 row in set (0.00 sec)
+```
+
+## 二：多表联合查询
+
+【扩展了解】
+
+#### 1.数据准备
+
+##### 表：company.employee6
+
+创建表：
+
+```shell
+MySQL [company]> create table employee6(
+ emp_id int auto_increment primary key not null,
+ emp_name varchar(50),
+ age int,
+ dept_id int);
+Query OK, 0 rows affected (0.65 sec)
+```
+
+查看表结构：
+
+```shell
+MySQL [company]> desc employee6;
++----------+-------------+------+-----+---------+----------------+
+| Field | Type | Null | Key | Default | Extra |
++----------+-------------+------+-----+---------+----------------+
+| emp_id | int(11) | NO | PRI | NULL | auto_increment |
+| emp_name | varchar(50) | YES | | NULL | |
+| age | int(11) | YES | | NULL | |
+| dept_id | int(11) | YES | | NULL | |
++----------+-------------+------+-----+---------+----------------+
+4 rows in set (0.00 sec)
+```
+
+插入模拟数据：
+
+```shell
+MySQL [company]> insert into employee6(emp_name,age,dept_id) values
+ ('',19,200),
+ ('tom',26,201),
+ ('jack',30,201),
+ ('alice',24,202),
+ ('robin',40,200),
+ ('xingdian',16,200),
+ ('natasha',28,204);
+```
+
+查看数据：
+
+```shell
+MySQL [company]> select * from employee6;
++--------+----------+------+---------+
+| emp_id | emp_name | age | dept_id |
++--------+----------+------+---------+
+| 1 | | 19 | 200 |
+| 2 | tom | 26 | 201 |
+| 3 | jack | 30 | 201 |
+| 4 | alice | 24 | 202 |
+| 5 | robin | 40 | 200 |
+| 6 | xingdian | 16 | 200 |
+| 7 | natasha | 28 | 204 |
++--------+----------+------+---------+
+7 rows in set (0.00 sec)
+```
+
+##### 表：company.department6
+
+创建表：
+
+```shell
+MySQL [company]> create table department6(
+ dept_id int,
+ dept_name varchar(100)
+ );
+Query OK, 0 rows affected (0.33 sec)
+```
+
+查看表结构：
+
+```shell
+MySQL [company]> desc department6;
++-----------+--------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-----------+--------------+------+-----+---------+-------+
+| dept_id | int(11) | YES | | NULL | |
+| dept_name | varchar(100) | YES | | NULL | |
++-----------+--------------+------+-----+---------+-------+
+2 rows in set (0.00 sec)
+```
+
+模拟插入数据：
+
+```shell
+MySQL [company]> insert into department6 values
+ (200,'hr'),
+ (201,'it'),
+ (202,'sale'),
+ (203,'fd');
+```
+
+查看数据：
+
+```shell
+MySQL [company]> select * from department6;
++---------+-----------+
+| dept_id | dept_name |
++---------+-----------+
+| 200 | hr |
+| 201 | it |
+| 202 | sale |
+| 203 | fd |
++---------+-----------+
+4 rows in set (0.01 sec)
+```
+
+#### 2.多表的连接查询
+
+ 交叉连接：生成笛卡尔积，它不使用任何匹配条件；交叉联接返回左表中的所有行，左表中的每一行与右表中的所有行组合
+
+ 内连接：只连接匹配的行
+
+ 外连接
+
+ 左连接：会显示左边表内所有的值，不论在右边表内匹不匹配
+
+ 右连接：会显示右边表内所有的值，不论在左边表内匹不匹配
+
+ 全外连接：包含左、右两个表的全部行
+
+##### 交叉连接
+
+```shell
+MySQL [company]> select employee6.emp_name,employee6.age,employee6.dept_id,department6.dept_name from employee6,department6;
++----------+------+---------+-----------+
+| emp_name | age | dept_id | dept_name |
++----------+------+---------+-----------+
+| | 19 | 200 | hr |
+| | 19 | 200 | it |
+| | 19 | 200 | sale |
+| | 19 | 200 | fd |
+| tom | 26 | 201 | hr |
+| tom | 26 | 201 | it |
+| tom | 26 | 201 | sale |
+| tom | 26 | 201 | fd |
+| jack | 30 | 201 | hr |
+| jack | 30 | 201 | it |
+| jack | 30 | 201 | sale |
+| jack | 30 | 201 | fd |
+| alice | 24 | 202 | hr |
+| alice | 24 | 202 | it |
+| alice | 24 | 202 | sale |
+| alice | 24 | 202 | fd |
+| robin | 40 | 200 | hr |
+| robin | 40 | 200 | it |
+| robin | 40 | 200 | sale |
+| robin | 40 | 200 | fd |
+| xingdian | 16 | 200 | hr |
+| xingdian | 16 | 200 | it |
+| xingdian | 16 | 200 | sale |
+| xingdian | 16 | 200 | fd |
+| natasha | 28 | 204 | hr |
+| natasha | 28 | 204 | it |
+| natasha | 28 | 204 | sale |
+| natasha | 28 | 204 | fd |
++----------+------+---------+-----------+
+28 rows in set (0.00 sec)
+```
+
+##### 内连接
+
+ 获取有部门的员工 (部门表中没有natasha所在的部门)
+
+```shell
+MySQL [company]> select employee6.emp_name,employee6.age,employee6.dept_id,department6.dept_name from employee6,department6 where employee6.dept_id=department6.dept_id;
++----------+------+---------+-----------+
+| emp_name | age | dept_id | dept_name |
++----------+------+---------+-----------+
+| | 19 | 200 | hr |
+| tom | 26 | 201 | it |
+| jack | 30 | 201 | it |
+| alice | 24 | 202 | sale |
+| robin | 40 | 200 | hr |
+| xingdian | 16 | 200 | hr |
++----------+------+---------+-----------+
+6 rows in set (0.00 sec)
+
+MySQL [company]> select employee6.emp_name,department6.dept_name from employee6 inner join department6 on employee6.dept_id=department6.dept_id;
++----------+-----------+
+| emp_name | dept_name |
++----------+-----------+
+| | hr |
+| tom | it |
+| jack | it |
+| alice | sale |
+| robin | hr |
+| xingdian | hr |
++----------+-----------+
+6 rows in set (0.01 sec)
+```
+
+##### 外连接
+
+语法：
+
+ SELECT 字段列表 FROM 表1 LEFT|RIGHT JOIN 表2 ON 表1.字段 = 表2.字段;
+
+注意：
+
+ 先用谁谁就是左
+
+###### 左连接 left join
+
+```shell
+找出所有员工及所属的部门，包括没有部门的员工
+MySQL [company]> select emp_id,emp_name,dept_name from employee6 left join department6 on employee6.dept_id = department6.dept_id;
++--------+----------+-----------+
+| emp_id | emp_name | dept_name |
++--------+----------+-----------+
+| 1 | | hr |
+| 5 | robin | hr |
+| 6 | xingdian | hr |
+| 2 | tom | it |
+| 3 | jack | it |
+| 4 | alice | sale |
+| 7 | natasha | NULL |
++--------+----------+-----------+
+7 rows in set (0.00 sec)
+```
+
+###### 右连接right join
+
+```
+找出所有部门包含的员工，包括空部门
+MySQL [company]> select emp_id,emp_name,dept_name from employee6 right join department6 on employee6.dept_id = department6.dept_id;
++--------+----------+-----------+
+| emp_id | emp_name | dept_name |
++--------+----------+-----------+
+| 1 | | hr |
+| 2 | tom | it |
+| 3 | jack | it |
+| 4 | alice | sale |
+| 5 | robin | hr |
+| 6 | xingdian | hr |
+| NULL | NULL | fd |
++--------+----------+-----------+
+7 rows in set (0.00 sec)
+```
+
+##### 全外连接
+
+```shell
+MySQL [company]> select * from employee6 full join department6;
++--------+----------+------+---------+---------+-----------+
+| emp_id | emp_name | age | dept_id | dept_id | dept_name |
++--------+----------+------+---------+---------+-----------+
+| 1 | | 19 | 200 | 200 | hr |
+| 1 | | 19 | 200 | 201 | it |
+| 1 | | 19 | 200 | 202 | sale |
+| 1 | | 19 | 200 | 203 | fd |
+| 2 | tom | 26 | 201 | 200 | hr |
+| 2 | tom | 26 | 201 | 201 | it |
+| 2 | tom | 26 | 201 | 202 | sale |
+| 2 | tom | 26 | 201 | 203 | fd |
+| 3 | jack | 30 | 201 | 200 | hr |
+| 3 | jack | 30 | 201 | 201 | it |
+| 3 | jack | 30 | 201 | 202 | sale |
+| 3 | jack | 30 | 201 | 203 | fd |
+| 4 | alice | 24 | 202 | 200 | hr |
+| 4 | alice | 24 | 202 | 201 | it |
+| 4 | alice | 24 | 202 | 202 | sale |
+| 4 | alice | 24 | 202 | 203 | fd |
+| 5 | robin | 40 | 200 | 200 | hr |
+| 5 | robin | 40 | 200 | 201 | it |
+| 5 | robin | 40 | 200 | 202 | sale |
+| 5 | robin | 40 | 200 | 203 | fd |
+| 6 | xingdian | 16 | 200 | 200 | hr |
+| 6 | xingdian | 16 | 200 | 201 | it |
+| 6 | xingdian | 16 | 200 | 202 | sale |
+| 6 | xingdian | 16 | 200 | 203 | fd |
+| 7 | natasha | 28 | 204 | 200 | hr |
+| 7 | natasha | 28 | 204 | 201 | it |
+| 7 | natasha | 28 | 204 | 202 | sale |
+| 7 | natasha | 28 | 204 | 203 | fd |
++--------+----------+------+---------+---------+-----------+
+28 rows in set (0.00 sec)
+```
+
+#### 3.复合条件连接查询
+
+##### 案例一
+
+ 找出公司所有部门中年龄大于25岁的员工
+
+ 以内连接的方式查询employee6和department6表，并且employee6表中的age字段值必须大于25
+
+```shell
+MySQL [company]> select emp_id,emp_name,dept_name FROM employee6,department6 WHERE employee6.dept_id = department6.dept_id AND age > 25;
++--------+----------+-----------+
+| emp_id | emp_name | dept_name |
++--------+----------+-----------+
+| 5 | robin | hr |
+| 2 | tom | it |
+| 3 | jack | it |
++--------+----------+-----------+
+3 rows in set (0.01 sec)
+```
+
+##### 案例二
+
+ 以内连接的方式查询employee6和department6表，并且以age字段的升序方式显示
+
+```shell
+MySQL [company]> select emp_id,emp_name,dept_name FROM employee6,department6 WHERE employee6.dept_id = department6.dept_id ORDER BY age asc;
++--------+----------+-----------+
+| emp_id | emp_name | dept_name |
++--------+----------+-----------+
+| 6 | xingdian | hr |
+| 1 | | hr |
+| 4 | alice | sale |
+| 2 | tom | it |
+| 3 | jack | it |
+| 5 | robin | hr |
++--------+----------+-----------+
+```
+
+#### 4.子查询
+
+ 子查询是将一个查询语句嵌套在另一个查询语句中
+
+ 内层查询语句的查询结果，可以为外层查询语句提供查询条件
+
+ 子查询中可以包含：IN、NOT IN等关键字；还可以包含比较运算符：= 、 !=、> 、<等
+
+##### 案例一
+
+ 带IN关键字的子查询；查询employee表，但dept_id必须在department表中出现过
+
+```shell
+MySQL [company]> select * from employee6 WHERE dept_id IN (select dept_id FROM department6);
++--------+----------+------+---------+
+| emp_id | emp_name | age | dept_id |
++--------+----------+------+---------+
+| 1 | | 19 | 200 |
+| 2 | tom | 26 | 201 |
+| 3 | jack | 30 | 201 |
+| 4 | alice | 24 | 202 |
+| 5 | robin | 40 | 200 |
+| 6 | xingdian | 16 | 200 |
++--------+----------+------+---------+
+6 rows in set (0.00 sec)
+```
+
+##### 案例二
+
+ 带比较运算符的子查询；查询年龄大于等于25岁员工所在部门（查询老龄化的部门）
+
+```shell
+MySQL [company]> select dept_id,dept_name FROM department6 WHERE dept_id IN (SELECT DISTINCT dept_id FROM employee6 WHERE age >=25);
++---------+-----------+
+| dept_id | dept_name |
++---------+-----------+
+| 201 | it |
+| 200 | hr |
++---------+-----------+
+2 rows in set (0.00 sec)
+```
\ No newline at end of file
diff --git a/第二章：数据库管理及数据类型.md b/第二章：数据库管理及数据类型.md
new file mode 100644
index 0000000..db37e92
--- /dev/null
+++ b/第二章：数据库管理及数据类型.md
@@ -0,0 +1,861 @@
+数据库管理及数据类型
+
+
+
+------
+
+## 一：数据类型
+
+#### 1.数值类型
+
+##### 整数类型
+
+ 整数类型：TINYINT SMALLINT MEDIUMINT INT BIGINT
+
+ 作用：用于存储用户的年龄、游戏的Level、经验值等
+
+
+
+##### 浮点数类型
+
+ 浮点数类型：FLOAT DOUBLE
+
+ 作用：用于存储用户的身高、体重、薪水等
+
+
+
+```shell
+float(5,3) 5宽度 3精度
+注意：
+ 宽度不算小数点
+ 宽度-精度=点前
+案例：
+MySQL [(none)]> create database diandian;
+Query OK, 1 row affected (0.00 sec)
+
+MySQL [(none)]> use diandian
+Database changed
+MySQL [diandian]> create table t1(id float(6,2));
+Query OK, 0 rows affected (0.24 sec)
+
+MySQL [diandian]> insert into t1 values('2.22');
+```
+
+##### 定点数类型
+
+ 定点数类型：DEC
+
+ 定点数在MySQL内部以字符串形式存储，比浮点数更精确，适合用来表示货币等精度高的数据
+
+##### 位类型
+
+ 位类型：BIT
+
+ BIT(M)可以用来存放多位二进制数，M范围从1~64，如果不写默认为1位
+
+#### 2.字符串类型
+
+ CHAR系列 CHAR VARCHAR
+
+ TEXT系列 TINYTEXT TEXT MEDIUMTEXT LONGTEXT
+
+ BLOB 系列 TINYBLOB BLOB MEDIUMBLOB LONGBLOB
+
+ BINARY系列 BINARY VARBINARY
+
+
+
+##### 枚举类型
+
+ 枚举类型：枚举列可以把一些不重复的字符串存储成一个预定义的集合
+
+```shell
+mysql> create table enum_table( e ENUM('fish','apple','dog'));
+Query OK, 0 rows affected (0.35 sec)
+mysql> insert into enum_table(e) values('fish');
+Query OK, 1 row affected (0.11 sec)
+
+mysql> select * from enum_table;
++------+
+| e |
++------+
+| fish |
++------+
+1 row in set (0.00 sec)
+
+mysql> insert into enum_table(e) values('nihao');
+ERROR 1265 (01000): Data truncated for column 'e' at row 1
+```
+
+##### 时间和日期类型
+
+ 时间和日期类型：DATE TIME DATETIME TIMESTAMP YEAR
+
+ 作用：用于存储用户的注册时间，文章的发布时间，文章的更新时间，员工的入职时间等
+
+
+
+```shell
+mysql> create table t8 (
+ id1 timestamp NOT NULL default CURRENT_TIMESTAMP,
+ id2 datetime default NULL
+);
+
+ timestamp 类型的列还有个特性：默认情况下，在 insert, update 数据时，timestamp 列会自动以当前时间（CURRENT_TIMESTAMP）填充/更新。“自动”的意思就是，你不去管它，MySQL 会替你去处理。
+
+mysql> insert into t8(id1) values('20180109000000');
+mysql> select * from t8;
++---------------------+------+
+| id1 | d2 |
++---------------------+------+
+| 2018-01-09 00:00:00 | NULL |
++---------------------+------+
+1 row in set (0.00 sec)
+
+扩展：
+select now();查看当前时间
+```
+
+## 二：表操作
+
+#### 1.案例
+
+表:：school.student1
+
+```
+字段 字段 字段
+id name sex age
+1 tom male 23 记录
+2 jack male 21 记录
+3 alice female 19 记录
+```
+
+语法：
+
+```shell
+create table 表名(自定义)(
+ 字段名1 类型[(宽度) 约束条件],
+ 字段名2 类型[(宽度) 约束条件],
+ 字段名3 类型[(宽度) 约束条件]
+)[存储引擎 字符集];
+==在同一张表中，字段名是不能相同
+==宽度和约束条件可选
+==字段名和类型是必须的
+```
+
+创建库表：
+
+```shell
+mysql> CREATE DATABASE school; //创建数据库school
+mysql> use school;
+mysql> create table student1(
+ id int,
+ name varchar(50),
+ sex enum('m','f'),
+ age int
+ );
+Query OK, 0 rows affected (0.03 sec)
+```
+
+查看库：
+
+```shell
+mysql> show tables;
++------------------+
+| Tables_in_school |
++------------------+
+| student1 |
++------------------+
+1 row in set (0.00 sec)
+```
+
+插入语法：
+
+```
+insert into 表名(字段1,字段2...) values(字段值列表...);
+```
+
+插入数据：
+
+```shell
+mysql> insert into student1(id,name,sex,age) values(1,'xingdia','m','26');
+```
+
+查看表结构：
+
+```shell
+mysql> desc student1;
++-------+---------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+---------------+------+-----+---------+-------+
+| id | int(11) | YES | | NULL | |
+| name | varchar(50) | YES | | NULL | |
+| sex | enum('m','f') | YES | | NULL | |
+| age | int(11) | YES | | NULL | |
++-------+---------------+------+-----+---------+-------+
+4 rows in set (0.00 sec)
+```
+
+查询数据：
+
+```shell
+mysql> select id,name,sex,age from student1; //查询表中所有字段的值
+Empty set (0.00 sec)
+
+mysql> select * from student1; /查询表中所有字段的值
+Empty set (0.00 sec)
+
+mysql> select name,age from student1; //查询表中指定字段的值
+Empty set (0.00 sec)
+```
+
+扩展插入：
+
+```shell
+mysql> insert into student1 values (1,'xingdian','m',33),(2,'alice','m',20),(3,'jack','m',40); //顺序插入
+Query OK, 3 rows affected (0.14 sec)
+Records: 3 Duplicates: 0 Warnings: 0
+
+mysql> insert into student1(name,age) values ('zhuzhu',10),('gougou',20); //只向指定的字段插入值
+Query OK, 2 rows affected (0.12 sec)
+Records: 2 Duplicates: 0 Warnings: 0
+```
+
+#### 2.案例
+
+表：school.student2
+
+```shell
+ 字段名 数据类型
+编号 id int
+姓名 name varchar(50)
+出生年份 born_year year
+生日 birthday date
+上课时间 class_time time
+注册时间 reg_time datetime
+```
+
+创建表：
+
+```shell
+mysql> create table student2(
+ id int,
+ name varchar(50),
+ born_year year,
+ birthday date,
+ class_time time,
+ reg_time datetime
+ );
+```
+
+插入数据：
+
+```shell
+mysql> insert into student2 values(1,'tom',now(),now(),now(),now());
+mysql> insert into student2 values(2,'jack',1982,19821120,123000,20140415162545);
+```
+
+表：school.student3
+
+```shell
+id id int
+姓名 name varchar(50)
+性别 sex enum('male','female')
+爱好 hobby set('music','book','game','disc')
+```
+
+创建表：
+
+```shell
+mysql> create table student3(
+ id int,
+ name varchar(50),
+ sex enum('male','female'),
+ hobby set('music','book','game','disc')
+ );
+```
+
+查看表结构：
+
+```shell
+mysql> desc student3;
+mysql> show create table student3\G
+```
+
+插入数据：
+
+```shell
+mysql> insert into student3 values (1,'tom','male','book,game');
+mysql> insert into student3 values (2,'jack','male','film');
+```
+
+注意：
+
+ DESCRIBE查看表结构
+
+```shell
+DESCRIBE 表名;
+DESC 表名;
+```
+
+ 查看表详细结构
+
+```shell
+SHOW CREATE TABLE 表名;
+```
+
+## 三：表完整性约束
+
+#### 1.作用
+
+ 用于保证数据的完整性和一致性
+
+#### 2.约束条件
+
+PRIMARY KEY (PK) 标识该字段为该表的主键，可以唯一的标识记录，不可以为空 UNIQUE + NOT NULL
+
+FOREIGN KEY (FK) 标识该字段为该表的外键，实现表与表（父表主键/子表1外键/子表2外键）之间的关联
+
+NOT NULL 标识该字段不能为空
+
+UNIQUE KEY (UK) 标识该字段的值是唯一的，可以为空，一个表中可以有多个UNIQUE KEY
+
+AUTO_INCREMENT 标识该字段的值自动增长（整数类型，而且为主键）
+
+DEFAULT 为该字段设置默认值
+
+注意：
+
+ 是否允许为空，默认NULL，可设置NOT NULL，字段不允许为空，必须赋值
+
+ 字段是否有默认值，缺省的默认值是NULL，如果插入记录时不给字段赋值，此字段使用默认值
+
+```shell
+MySQL [(none)]> sex enum('male','female') not null default 'male'
+MySQL [(none)]> age int unsigned NOT NULL default 20 必须为正值（无符号） 不允许为空 默认是20
+```
+
+ 是否是key 主键 primary key 外键 forengn key
+
+#### 3.NOT NULL
+
+表：school.student4
+
+创建表：（注意前提需要有库）
+
+```shell
+mysql> create table school.student4(
+ id int not null,
+ name varchar(50) not null,
+ sex enum('m','f') default 'm' not null,
+ age int unsigned default 18 not null,
+ hobby set('music','disc','dance','book') default 'book,dance'
+ );
+```
+
+插入数据：（注意观察查询到的数据）
+
+```shell
+MySQL [(none)]> insert into school.student4(id,name) values(2,'robin');
+Query OK, 1 row affected (0.08 sec)
+
+MySQL [(none)]> select * from school.student4;
++----+-------+-----+-----+------------+
+| id | name | sex | age | hobby |
++----+-------+-----+-----+------------+
+| 2 | robin | m | 18 | dance,book |
++----+-------+-----+-----+------------+
+1 row in set (0.00 sec)
+```
+
+注意报错的原因：
+
+```shell
+MySQL [(none)]> insert into school.student4 values(3,NULL,'m',40,'book');
+ERROR 1048 (23000): Column 'name' cannot be null
+```
+
+#### 4.唯一约束
+
+作用：
+
+ MySQL索引的建立对于MySQL的高效运行是很重要的，索引可以大大提高MySQL的检索速度
+
+表：company.department1
+
+创建表：
+
+```shell
+MySQL [(none)]> create database company;
+Query OK, 1 row affected (0.01 sec)
+MySQL [(none)]> CREATE TABLE company.department1 (dept_id INT,dept_name VARCHAR(30) UNIQUE,comment VARCHAR(50));
+Query OK, 0 rows affected (0.34 sec)
+```
+
+查看表结构：
+
+```shell
+MySQL [(none)]> desc company.department1;
++-----------+-------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-----------+-------------+------+-----+---------+-------+
+| dept_id | int(11) | YES | | NULL | |
+| dept_name | varchar(30) | YES | UNI | NULL | |
+| comment | varchar(50) | YES | | NULL | |
++-----------+-------------+------+-----+---------+-------+
+3 rows in set (0.00 sec)
+```
+
+数据插入：（注意查看插入数据时的提示）
+
+```shell
+MySQL [(none)]> insert into company.department1 values ("1","xingdian","hr");
+Query OK, 1 row affected (0.04 sec)
+
+MySQL [(none)]> insert into company.department1 values ("1","xingdian","hr");
+ERROR 1062 (23000): Duplicate entry 'xingdian' for key 'dept_name'
+```
+
+#### 5.主键约束
+
+注意：primary key 字段的值是不允许重复，且不允许不NULL（UNIQUE + NOT NULL）
+
+表：school.student6
+
+创建表：
+
+```shell
+MySQL [(none)]> create table school.student6(
+ id int primary key not null auto_increment,
+ name varchar(50) not null,
+ sex enum('male','female') not null default 'male',
+ age int not null default 18
+ );
+Query OK, 0 rows affected (0.47 sec)
+```
+
+插入数据：
+
+```shell
+MySQL [(none)]> insert into school.student6 values (1,'alice','female',22);
+Query OK, 1 row affected (0.18 sec)
+
+MySQL [(none)]> insert into school.student6(name,sex,age) values
+ -> ('jack','male',19),
+ -> ('tom','male',23);
+Query OK, 2 rows affected (0.14 sec)
+Records: 2 Duplicates: 0 Warnings: 0
+
+MySQL [(none)]> select * from school.student6;
++----+-------+--------+-----+
+| id | name | sex | age |
++----+-------+--------+-----+
+| 1 | alice | female | 22 |
+| 2 | jack | male | 19 |
+| 3 | tom | male | 23 |
++----+-------+--------+-----+
+3 rows in set (0.00 sec)
+
+```
+
+## 四：修改表
+
+语法格式：
+
+修改表名
+
+ ALTER TABLE 表名 RENAME 新表名;
+
+增加字段
+
+ ALTER TABLE 表名
+
+ ADD 字段名 数据类型 [完整性约束条件…],
+
+ ADD 字段名 数据类型 [完整性约束条件…];
+
+ ALTER TABLE 表名
+
+ ADD 字段名 数据类型 [完整性约束条件…] AFTER 字段名;
+删除字段
+
+ ALTER TABLE 表名 DROP 字段名;
+
+修改字段
+
+ ALTER TABLE 表名 MODIFY 字段名 数据类型 [完整性约束条件…];
+
+ ALTER TABLE 表名 CHANGE 旧字段名 新字段名 旧数据类型 [完整性约束条件…];
+
+ ALTER TABLE 表名 CHANGE 旧字段名 新字段名 新数据类型 [完整性约束条件…];
+
+#### 1.修改数据库引擎
+
+```shell
+mysql> alter table service engine=innodb; //engine=myisam|memory|....
+```
+
+#### 2.添加字段
+
+```shell
+mysql> create table student10 (id int);
+mysql> alter table student10 add name varchar(20) not null, add age int not null default 22;
+
+mysql> alter table student10 add stu_num int not null after name; //添加name字段之后
+
+mysql> alter table student10 add sex enum('male','female') default 'male' first; //添加到最前面
+```
+
+#### 3.删除字段
+
+```shell
+mysql> alter table student10 drop sex;
+```
+
+#### 4.修改字段类型
+
+```shell
+MySQL [school]> desc student10;
++-------+---------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+---------+------+-----+---------+-------+
+| id | int(11) | YES | | NULL | |
+| age | int(11) | YES | | NULL | |
++-------+---------+------+-----+---------+-------+
+2 rows in set (0.01 sec)
+
+MySQL [school]> alter table student10 modify age tinyint not null ;
+Query OK, 0 rows affected (0.04 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+-------+
+| id | int(11) | YES | | NULL | |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+-------+
+2 rows in set (0.00 sec)
+
+MySQL [school]> alter table student10 modify id int not null primary key ; ////修改字段类型、约束、主键
+Query OK, 0 rows affected (0.02 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+-------+
+| id | int(11) | NO | PRI | NULL | |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+-------+
+```
+
+#### 5.增加约束
+
+```shell
+MySQL [school]> alter table student10 modify id int not null primary key ;
+Query OK, 0 rows affected (0.02 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+-------+
+| id | int(11) | NO | PRI | NULL | |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+-------+
+2 rows in set (0.00 sec)
+
+MySQL [school]> alter table student10 modify id int not null primary key auto_increment;
+ERROR 1068 (42000): Multiple primary key defined //错误，该字段已经是primary key
+
+MySQL [school]> alter table student10 modify id int not null auto_increment;
+Query OK, 0 rows affected (0.04 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+----------------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+----------------+
+| id | int(11) | NO | PRI | NULL | auto_increment |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+----------------+
+```
+
+#### 6.增加主键
+
+```shell
+MySQL [school]> desc student1;
++-------+---------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+---------+------+-----+---------+-------+
+| id | int(11) | YES | | NULL | |
+| age | int(11) | YES | | NULL | |
+| name | char(1) | YES | | NULL | |
++-------+---------+------+-----+---------+-------+
+3 rows in set (0.00 sec)
+
+MySQL [school]> alter table student1 add primary key(id);
+
+MySQL [school]> desc student1;
++-------+---------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+---------+------+-----+---------+-------+
+| id | int(11) | NO | PRI | NULL | |
+| age | int(11) | YES | | NULL | |
+| name | char(1) | YES | | NULL | |
++-------+---------+------+-----+---------+-------+
+3 rows in set (0.00 sec)
+```
+
+#### 7.修改主键和自增
+
+```shell
+MySQL [school]> alter table student1 modify id int auto_increment;
+Query OK, 0 rows affected (0.03 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student1;
++-------+---------+------+-----+---------+----------------+
+| Field | Type | Null | Key | Default | Extra |
++-------+---------+------+-----+---------+----------------+
+| id | int(11) | NO | PRI | NULL | auto_increment |
+| age | int(11) | YES | | NULL | |
+| name | char(1) | YES | | NULL | |
++-------+---------+------+-----+---------+----------------+
+```
+
+#### 8.删除主键
+
+```shell
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+----------------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+----------------+
+| id | int(11) | NO | PRI | NULL | auto_increment |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+----------------+
+2 rows in set (0.00 sec)
+
+MySQL [school]> alter table student10 drop primary key;
+ERROR 1075 (42000): Incorrect table definition; there can be only one auto column and it must be defined as a key
+
+删除自增
+ySQL [school]> alter table student10 modify id int not null;
+Query OK, 0 rows affected (0.04 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+-------+
+| id | int(11) | NO | PRI | NULL | |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+-------+
+
+MySQL [school]> alter table student10 drop primary key;
+Query OK, 0 rows affected (0.03 sec)
+Records: 0 Duplicates: 0 Warnings: 0
+
+MySQL [school]> desc student10;
++-------+------------+------+-----+---------+-------+
+| Field | Type | Null | Key | Default | Extra |
++-------+------------+------+-----+---------+-------+
+| id | int(11) | NO | | NULL | |
+| age | tinyint(4) | NO | | NULL | |
++-------+------------+------+-----+---------+-------+
+2 rows in set (0.00 sec)
+```
+
+#### 9.复制表
+
+复制表结构＋记录 （key不会复制: 主键、外键和索引）复制表结构/记录+表结构，不会将Key复制
+
+```shell
+mysql> create table new_service select * from service;
+```
+
+只复制表结构
+
+```shell
+mysql> create table new1_service select * from service where 1=2; //条件为假，查不到任何记录
+```
+
+可以复制主键,只复制表结构
+
+```shell
+mysql> create table t4 like employees;
+```
+
+#### 10.删除表
+
+```shell
+mysql> DROP TABLE 表名;
+```
+
+#### 11.修改数据表中字段的值
+
+语法：
+
+ Update 表名 set 列名=值where 条件
+
+```shell
+mysql> update student set name='123' where id=1;
+```
+
+删除某一行：
+
+ delete from 表名 where id=1
+
+```shell
+mysql> delete from type where id=1;
+```
+
+## 五：库操作
+
+#### 1.简介
+
+ 系统自带库的含义及作用
+
+```shell
+MySQL [(none)]> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| mysql |
+| performance_schema |
+| sys |
++--------------------+
+```
+
+information_schema：虚拟库，主要存储了系统中的一些数据库对象的信息，例如用户表信息、列信息、权限信息、字符信息等
+
+performance_schema：主要存储数据库服务器的性能参数
+
+mysql：授权库，主要存储系统用户的权限信息
+
+sys：主要存储数据库服务器的性能参数
+
+注意：information_schema
+
+ SCHEMATA 存放的是系统中的库
+
+```shell
+MySQL [information_schema]> select * from information_schema.SCHEMATA;
++--------------+--------------------+----------------------------+------------------------+----------+
+| CATALOG_NAME | SCHEMA_NAME | DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME | SQL_PATH |
++--------------+--------------------+----------------------------+------------------------+----------+
+| def | information_schema | utf8 | utf8_general_ci | NULL |
+| def | mysql | latin1 | latin1_swedish_ci | NULL |
+| def | performance_schema | utf8 | utf8_general_ci | NULL |
+| def | school | latin1 | latin1_swedish_ci | NULL |
+| def | sys | utf8 | utf8_general_ci | NULL |
++--------------+--------------------+----------------------------+------------------------+----------+
+
+目录_名称
+实际库_名称
+默认_字符_设置_名称
+默认_分类_名称
+```
+
+ TABLES 存储表名
+
+```shell
+MySQL [information_schema]> select * from information_schema.TABLES\G
+*************************** 283. row ***************************
+ TABLE_CATALOG: def
+ TABLE_SCHEMA: xingdian
+ TABLE_NAME: t1
+ TABLE_TYPE: BASE TABLE
+ ENGINE: InnoDB
+ VERSION: 10
+ ROW_FORMAT: Dynamic
+ TABLE_ROWS: 1
+ AVG_ROW_LENGTH: 16384
+ DATA_LENGTH: 16384
+MAX_DATA_LENGTH: 0
+ INDEX_LENGTH: 0
+ DATA_FREE: 0
+ AUTO_INCREMENT: NULL
+ CREATE_TIME: 2022-09-22 08:18:38
+ UPDATE_TIME: 2022-09-22 08:18:54
+ CHECK_TIME: NULL
+TABLE_COLLATION: latin1_swedish_ci
+ CHECKSUM: NULL
+ CREATE_OPTIONS:
+ TABLE_COMMENT:
+283 rows in set (0.02 sec)
+```
+
+ COLUMNS 存储字段
+
+```shell
+*************************** 3083. row ***************************
+ TABLE_CATALOG: def
+ TABLE_SCHEMA: xingdian
+ TABLE_NAME: t1
+ COLUMN_NAME: id
+ ORDINAL_POSITION: 1
+ COLUMN_DEFAULT: NULL
+ IS_NULLABLE: YES
+ DATA_TYPE: int
+CHARACTER_MAXIMUM_LENGTH: NULL
+ CHARACTER_OCTET_LENGTH: NULL
+ NUMERIC_PRECISION: 10
+ NUMERIC_SCALE: 0
+ DATETIME_PRECISION: NULL
+ CHARACTER_SET_NAME: NULL
+ COLLATION_NAME: NULL
+ COLUMN_TYPE: int(11)
+ COLUMN_KEY:
+ EXTRA:
+ PRIVILEGES: select,insert,update,references
+ COLUMN_COMMENT:
+ GENERATION_EXPRESSION:
+3083 rows in set (0.03 sec)
+```
+
+#### 2.创建库
+
+方案一：交互式操作
+
+```shell
+mysql> create database xingdian;
+```
+
+数据库命名规则：
+
+ 区分大小写
+
+ 唯一性
+
+ 不能使用关键字如 create select
+
+ 不能单独使用数字
+
+方案二：非交互式
+
+```shell
+mysql -u root -pQianFeng@123 -e "create database diandian"
+```
+
+#### 3.查看数据库
+
+```shell
+mysql> show databases;
+mysql> show create database xingdian;
+mysql> select database(); 查看当前所在的库
+```
+
+#### 4.切换数据库
+
+```shell
+mysql> use xingdian;
+```
+
+#### 5.删除数据库
+
+```shell
+mysql> DROP DATABASE 数据库名;
+```
diff --git a/第五章：权限管理及数据备份与恢复.md b/第五章：权限管理及数据备份与恢复.md
new file mode 100644
index 0000000..3cb6c07
--- /dev/null
+++ b/第五章：权限管理及数据备份与恢复.md
@@ -0,0 +1,1228 @@
+权限管理及数据备份与恢复
+
+
+
+------
+
+## 一：权限管理
+
+#### 1.权限级别
+
+ Global level：系统级，所有库，所有表的权限
+
+ Database level：某个数据库中的所有表的权限
+
+ Table level：库中的某个表的权限
+
+ Column level：表中的某个字段的权限
+
+ procs level：某个存储过程的权限
+
+ proxies level：代理服务器的权限
+
+#### 2.查看权限记录表
+
+ 因为超级管理员默认已经设置；所以直接查询权限即可
+
+##### Global level
+
+```
+ mysql> select * from mysql.user\G
+*************************** 1. row ***************************
+ Host: localhost
+ User: root
+ Select_priv: Y
+ Insert_priv: Y
+ Update_priv: Y
+ Delete_priv: Y
+ Create_priv: Y
+ Drop_priv: Y
+ Reload_priv: Y
+ Shutdown_priv: Y
+ Process_priv: Y
+ File_priv: Y
+ Grant_priv: Y
+ References_priv: Y
+ Index_priv: Y
+ Alter_priv: Y
+ Show_db_priv: Y
+ Super_priv: Y
+ Create_tmp_table_priv: Y
+ Lock_tables_priv: Y
+ Execute_priv: Y
+ Repl_slave_priv: Y
+ Repl_client_priv: Y
+ Create_view_priv: Y
+ Show_view_priv: Y
+ Create_routine_priv: Y
+ Alter_routine_priv: Y
+ Create_user_priv: Y
+ Event_priv: Y
+ Trigger_priv: Y
+Create_tablespace_priv: Y
+ ssl_type:
+ ssl_cipher:
+ x509_issuer:
+ x509_subject:
+ max_questions: 0
+ max_updates: 0
+ max_connections: 0
+ max_user_connections: 0
+ plugin: mysql_native_password
+ authentication_string: *B1DD4ADE47888D9AEC4D705C85230F1B52D2A817
+ password_expired: N
+ password_last_changed: 2022-09-25 14:44:38
+ password_lifetime: NULL
+ account_locked: N
+```
+
+字段介绍：
+
+```shell
+用户字段：root
+权限字段：Select_priv
+安全字段：*B1DD4ADE47888D9AEC4D705C85230F1B52D2A817
+
+Select_priv：查询权限
+Insert_priv：插入权限
+Update_priv：更新权限
+Delete_priv：删除权限
+......
+```
+
+##### Database level
+
+```shell
+mysql> select * from mysql.db\G;
+*************************** 1. row ***************************
+ Host: localhost
+ Db: performance_schema
+ User: mysql.session
+ Select_priv: Y
+ Insert_priv: N
+ Update_priv: N
+ Delete_priv: N
+ Create_priv: N
+ Drop_priv: N
+ Grant_priv: N
+ References_priv: N
+ Index_priv: N
+ Alter_priv: N
+Create_tmp_table_priv: N
+ Lock_tables_priv: N
+ Create_view_priv: N
+ Show_view_priv: N
+ Create_routine_priv: N
+ Alter_routine_priv: N
+ Execute_priv: N
+ Event_priv: N
+ Trigger_priv: N
+```
+
+测试库权限：
+
+```shell
+mysql> create database t1;
+Query OK, 1 row affected (0.00 sec)
+
+mysql> grant all on t1.* to 't1'@'localhost' identified by 'QianFeng@123';
+Query OK, 0 rows affected, 1 warning (0.00 sec)
+```
+
+查看：
+
+```
+mysql> select * from mysql.db\G
+*************************** 3. row ***************************
+ Host: localhost
+ Db: t1
+ User: t1
+ Select_priv: Y
+ Insert_priv: Y
+ Update_priv: Y
+ Delete_priv: Y
+ Create_priv: Y
+ Drop_priv: Y
+ Grant_priv: N
+ References_priv: Y
+ Index_priv: Y
+ Alter_priv: Y
+Create_tmp_table_priv: Y
+ Lock_tables_priv: Y
+ Create_view_priv: Y
+ Show_view_priv: Y
+ Create_routine_priv: Y
+ Alter_routine_priv: Y
+ Execute_priv: Y
+ Event_priv: Y
+ Trigger_priv: Y
+3 rows in set (0.00 sec)
+```
+
+验证：
+
+```shell
+[root@xingdian ~]# mysql -u t1 -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 4
+Server version: 5.7.39-log MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| t1 |
++--------------------+
+2 rows in set (0.00 sec)
+
+```
+
+##### Table level
+
+```shell
+mysql> select * from mysql.tables_priv\G;
+*************************** 1. row ***************************
+ Host: localhost
+ Db: mysql
+ User: mysql.session
+ Table_name: user
+ Grantor: boot@connecting host
+ Timestamp: 0000-00-00 00:00:00
+ Table_priv: Select
+Column_priv:
+*************************** 2. row ***************************
+ Host: localhost
+ Db: sys
+ User: mysql.sys
+ Table_name: sys_config
+ Grantor: root@localhost
+ Timestamp: 2022-09-25 14:40:58
+ Table_priv: Select
+Column_priv:
+2 rows in set (0.00 sec)
+```
+
+创建库表验证：
+
+```shell
+mysql> create database t2;
+Query OK, 1 row affected (0.00 sec)
+
+mysql> use t2;
+Database changed
+mysql> create table u1(id int);
+Query OK, 0 rows affected (0.01 sec)
+
+mysql> insert into u1 values (1);
+Query OK, 1 row affected (0.01 sec)
+
+mysql> grant all on t2.u1 to 't2'@'localhost' identified by 'QianFeng@123';
+Query OK, 0 rows affected, 1 warning (0.00 sec)
+
+mysql> create table u2(id int);
+Query OK, 0 rows affected (0.01 sec)
+
+mysql> show tables;
++--------------+
+| Tables_in_t2 |
++--------------+
+| u1 |
+| u2 |
++--------------+
+2 rows in set (0.00 sec)
+```
+
+权限查看：
+
+```shell
+mysql> select * from mysql.tables_priv\G;
+*************************** 3. row ***************************
+ Host: localhost
+ Db: t2
+ User: t2
+ Table_name: u1
+ Grantor: root@localhost
+ Timestamp: 0000-00-00 00:00:00
+ Table_priv: Select,Insert,Update,Delete,Create,Drop,References,Index,Alter,Create View,Show view,Trigger
+Column_priv:
+3 rows in set (0.00 sec)
+```
+
+验证：（登录t2账户，看到u1表，看不到u2代表权限成功）
+
+```shell
+[root@xingdian ~]# mysql -u t2 -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 6
+Server version: 5.7.39-log MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| t2 |
++--------------------+
+2 rows in set (0.00 sec)
+
+mysql> use t2;
+Reading table information for completion of table and column names
+You can turn off this feature to get a quicker startup with -A
+
+Database changed
+mysql> show tables;
++--------------+
+| Tables_in_t2 |
++--------------+
+| u1 |
++--------------+
+1 row in set (0.00 sec)
+```
+
+##### Column level
+
+```shell
+[root@xingdian ~]# mysql -uroot -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 7
+Server version: 5.7.39-log MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> select * from mysql.columns_priv\G;
+Empty set (0.00 sec)
+
+mysql> insert into mysql.columns_priv(host,db,user,table_name,column_name,column_priv) values('%','t2','t2','u1','id','select');
+Query OK, 1 row affected (0.00 sec)
+
+mysql> select * from mysql.columns_priv\G;
+*************************** 1. row ***************************
+ Host: %
+ Db: t2
+ User: t2
+ Table_name: u1
+Column_name: id
+ Timestamp: 2022-09-25 15:34:05
+Column_priv: Select
+1 row in set (0.00 sec)
+```
+
+注意：
+
+ 前提是有库，有表，有权限
+
+## 二：用户管理
+
+#### 1.登录和退出
+
+```shell
+[root@xingdian ~]# mysql -h 192.168.18.160 -P 30042 -u root -pmysql -e "show databases;"
+[root@xingdian ~]# mysql -h 192.168.18.160 -P 30042 -u root -pmysql mysql -e "show tables;"
+
+ -h 指定主机名 【默认为localhost】
+ -P MySQL服务器端口 【默认3306】
+ -u 指定用户名 【默认root】
+ -p 指定登录密码 【默认为空密码】
+ 此处mysql为指定登录的数据库
+ -e 接SQL语句 (在脚本中使用)
+
+```
+
+#### 2.创建用户
+
+方式一：
+
+```shell
+mysql> create user xingdian;
+ERROR 1819 (HY000): Your password does not satisfy the current policy requirements
+注意：
+ 该报错是因为密码强度问题，取消密码强度即可创建用户
+
+mysql> create user xingdian@'%' identified by 'QianFeng@123';
+Query OK, 0 rows affected (0.00 sec)
+```
+
+方式二：
+
+```shell
+mysql> grant all on *.* to 'diange'@'localhost' identified by 'QianFeng@123';
+Query OK, 0 rows affected, 1 warning (0.00 sec)
+```
+
+注意：
+
+ 该方式采用授权的方式
+
+ ALL 所有权限 select 单独某一个权限（多个权限用逗号隔开）
+
+```shell
+mysql> grant select on *.* to 'dianye'@'localhost' identified by 'QianFeng@123';
+Query OK, 0 rows affected, 1 warning (0.00 sec)
+```
+
+```shell
+*.* 所有的库所有的表 也可以单独某一个库某一个表
+```
+
+```shell
+xingdian@localhost 用户有则授权无则创建 localhost % 10.19.40.% 10.19.40.11
+```
+
+#### 3.删除用户
+
+方式一：
+
+```shell
+MySQL [(none)]> Drop user xingdian@'%';
+Query OK, 0 rows affected (0.00 sec)
+```
+
+方法二：
+
+```shell
+MySQL [(none)]> delete from mysql.user where user='diandian' AND Host='%';
+Query OK, 1 row affected (0.00 sec)
+```
+
+#### 4.修改密码
+
+方式一：
+
+```shell
+[root@xingdian ~]# mysqladmin -uroot -p'123' password 'new_password' //123为旧密码
+```
+
+方式二：
+
+```shell
+MySQL [(none)]> update mysql.user set authentication_string=password(123456) where user='diange' And Host='%';
+```
+
+注意：
+
+ 刷新授权表后生效：flush privileges
+
+自己设置自己密码：
+
+```shell
+MySQL [(none)]> set password='123';
+Query OK, 0 rows affected (0.00 sec)
+```
+
+root用户修改其他用户密码：
+
+方法一：
+
+```shell
+mysql> SET PASSWORD FOR user3@'localhost'='new_password';
+```
+
+方法二：
+
+```shell
+UPDATE mysql.user SET authentication_string=password('new_password') WHERE user='user3' AND host='localhost';
+```
+
+#### 5.查看密码策略
+
+```shell
+mysql> SHOW VARIABLES LIKE 'validate_password%';
++--------------------------------------+--------+
+| Variable_name | Value |
++--------------------------------------+--------+
+| validate_password_check_user_name | OFF |
+| validate_password_dictionary_file | |
+| validate_password_length | 8 |
+| validate_password_mixed_case_count | 1 |
+| validate_password_number_count | 1 |
+| validate_password_policy | MEDIUM |
+| validate_password_special_char_count | 1 |
++--------------------------------------+--------+
+7 rows in set (0.00 sec)
+```
+
+参数解释：
+
+ validate_password_dictionary_file 指定密码验证的文件路径
+
+ validate_password_length 密码最小长度
+
+ validate_password_mixed_case_count 密码至少要包含的小写字母个数和大写字母个数
+
+ validate_password_number_count 密码至少要包含的数字个数
+
+ validate_password_policy 密码强度检查等级，对应等级为：0/LOW、1/MEDIUM、2/STRONG,默认为1
+
+ 0/LOW：只检查长度
+
+ 1/MEDIUM：检查长度、数字、大小写、特殊字符
+
+ 2/STRONG：检查长度、数字、大小写、特殊字符字典文件
+
+ validate_password_special_char_count密码至少要包含的特殊字符数
+
+修改密码策略：
+
+```shell
+mysql> SHOW VARIABLES LIKE 'validate_password%';
++--------------------------------------+--------+
+| Variable_name | Value |
++--------------------------------------+--------+
+| validate_password_check_user_name | OFF |
+| validate_password_dictionary_file | |
+| validate_password_length | 8 |
+| validate_password_mixed_case_count | 1 |
+| validate_password_number_count | 1 |
+| validate_password_policy | MEDIUM |
+| validate_password_special_char_count | 1 |
++--------------------------------------+--------+
+7 rows in set (0.00 sec)
+
+mysql> set global validate_password_length=4;
+Query OK, 0 rows affected (0.00 sec)
+
+mysql> SHOW VARIABLES LIKE 'validate_password%';
++--------------------------------------+--------+
+| Variable_name | Value |
++--------------------------------------+--------+
+| validate_password_check_user_name | OFF |
+| validate_password_dictionary_file | |
+| validate_password_length | 4 |
+| validate_password_mixed_case_count | 1 |
+| validate_password_number_count | 1 |
+| validate_password_policy | MEDIUM |
+| validate_password_special_char_count | 1 |
++--------------------------------------+--------+
+7 rows in set (0.00 sec)
+```
+
+关闭密码策略：
+
+```
+修改配置文件，添加以下参数：
+validate_password=off
+```
+
+## 三：数据备份及恢复
+
+#### 1.概述
+
+ 所有备份数据都应放在非数据库本地，而且建议有多份副本
+
+备份： 能够防止由于机械故障以及人为误操作带来的数据丢失，例如将数据库文件保存在了其它地方
+
+冗余： 数据有多份冗余，但不等备份，只能防止机械故障还来的数据丢失，例如主备模式、数据库集群
+
+备份考虑的因素：
+
+ 数据的一致性
+
+ 服务的可用性
+
+分类：
+
+ 逻辑备份
+
+ 备份的是建表、建库、插入等操作所执行SQL语句；适用于中小型数据库，效率相对较低（mysqldump）
+
+ 物理备份
+
+ 直接复制数据库文件，适用于大型数据库环境，不受存储引擎的限制，但不能恢复到不同的MySQL版本（tar、xtrabackup）
+
+备份方式分类：
+
+ 完全备份
+
+ 备份所有数据
+
+ 增量备份
+
+ 每次备份上一次备份到现在产生的新数据
+
+
+
+ 差异备份
+
+ 只备份跟完整备份不一样的
+
+
+
+#### 2.tar备份
+
+ 注意：备份期间，服务不可用
+
+备份过程：完全物理备份
+
+ 停止数据库
+
+```shell
+[root@xingdian ~]# systemctl stop mysqld
+```
+
+ tar备份数据
+
+```shell
+[root@xingdian ~]# mkdir /backup
+[root@xingdian ~]# cd /var/lib/mysql
+[root@xingdian ~]# tar -zcvf /backup/`date +%F`-mysql-all.tar.gz ./*
+```
+
+ 启动数据库（备份完成后启动数据库，继续为其他服务提供服务）
+
+```shell
+[root@xingdian ~]# systemctl start mysqld
+```
+
+恢复过程：模拟数据丢失，恢复数据
+
+ 停止数据库
+
+```shell
+[root@xingdian ~]# systemctl stop mysqld
+```
+
+ 清理环境
+
+```shell
+[root@xingdian ~]# rm -rf /var/lib/mysql/*
+```
+
+ 导入备份数据
+
+```shell
+[root@xingdian ~]# tar -xvf /backup/2019-08-20-mysql-all.tar.gz -C /usr/lib/mysql
+[root@xingdian ~]# chown mysql.mysql /var/lib/mysql/* -R
+```
+
+ 启动数据库（恢复后验证数据是否恢复成功）
+
+```shell
+[root@xingdian ~]# systemctl start mysqld
+```
+
+#### 3.xtrabackup备份
+
+简介：
+
+ percona-xtrabackup是开源免费的支持MySQL 数据库热备份的软件；能对InnoDB和XtraDB存储引擎的数据库非阻塞地备份；它不暂停服务创建Innodb热备份；为mysql做增量备份；在mysql服务器之间做在线表迁移；使创建replication更加容易；备份mysql而不增加服务器的负载
+
+
+
+安装软件：
+
+```shell
+[root@xingdian ~]# yum install https://repo.percona.com/yum/percona-release-latest.noarch.rpm -y
+[root@xingdian ~]# yum install percona-xtrabackup-24 -y
+```
+
+##### 完整备份
+
+ 创建备份目录：
+
+```shell
+[root@xingdian ~]# mkdir -p /xtrabackup/full/
+```
+
+ 备份：
+
+```shell
+[root@xingdian ~]# innobackupex --user=root --password='QianFeng@123' /xtrabackup/full/
+```
+
+ 查看备份数据：
+
+```shell
+[root@xingdian ~]# ls /xtrabackup/full/
+2022-09-25_19-40-47
+```
+
+ 模拟数据丢失数据恢复：（以下操作模拟数据丢失）
+
+丢失前数据库中的数据：
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 7
+Server version: 5.7.39 MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| mysql |
+| performance_schema |
+| sys |
+| t1 |
++--------------------+
+5 rows in set (0.00 sec)
+```
+
+数据丢失：
+
+```shell
+[root@xingdian ~]# systemctl stop mysqld
+[root@xingdian ~]# rm -rf /var/lib/mysql/*
+[root@xingdian ~]# rm -rf /var/log/mysqld.log
+[root@xingdian ~]# rm -rf /var/log/mysql-slow/slow.log (有则删除，无则不需要操作)
+```
+
+ 恢复前的验证：
+
+```shell
+[root@xingdian ~]# innobackupex --apply-log /xtrabackup/full/2022-09-25_19-40-47/
+```
+
+ 恢复之前需要确认配置文件内有数据库目录指定，不然xtrabackup不知道恢复到哪里
+
+```shell
+[root@xingdian ~]# cat /etc/my.cnf
+datadir=/var/lib/mysql
+```
+
+ 恢复数据：
+
+```shell
+[root@xingdian ~]# innobackupex --copy-back /xtrabackup/full/2022-09-25_19-40-47/
+```
+
+ 修改权限：
+
+```shell
+[root@xingdian ~]# chown mysql.mysql /var/lib/mysql -R
+```
+
+ 启动服务：
+
+```shell
+[root@xingdian ~]# systemctl start mysqld
+```
+
+ 验证：
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 2
+Server version: 5.7.39 MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| mysql |
+| performance_schema |
+| sys |
+| t1 |
++--------------------+
+5 rows in set (0.00 sec)
+```
+
+##### 增量备份
+
+原理：每次备份上一次备份到现在产生的新数据
+
+注意：在进行增量备份前先进行完整备份
+
+案例：周一进行全备，周二到周天进行增量备份
+
+ 完整备份：（周一）
+
+```shell
+[root@xingdian ~]# innobackupex --user=root --password='QianFeng@123' /xtrabackup/full
+```
+
+ 创建增量备份存放数据目录：
+
+```shell
+[root@xingdian ~]# mkdir /xtrabackup/zeng -p
+```
+
+ 模拟数据增加（略）
+
+ 第一次增量备份：（周二）
+
+```shell
+[root@xingdian ~]# innobackupex --user=root --password='QianFeng@123' --incremental /xtrabackup/zeng/ --incremental-basedir=/xtrabackup/full/2022-09-25_19-40-47/
+
+第一次增量备份的数据：
+[root@xingdian ~]# ls /xtrabackup/zeng/
+2022-09-25_19-56-00
+```
+
+ 模拟数据增加（略）
+
+ 第二次增量备份：（周三）
+
+```shell
+[root@xingdian ~]# innobackupex --user=root --password='QianFeng@123' --incremental /xtrabackup/zeng/ --incremental-basedir=/xtrabackup/zeng/2022-09-25_19-56-00/
+
+第二次增量备份的数据：
+[root@xingdian ~]# ls /xtrabackup/zeng/
+2022-09-25_19-56-00 2022-09-25_19-58-12
+```
+
+ 后面的增量备份重复上面的操作（略）
+
+增量备份数据恢复流程：（需要模拟数据的丢失）
+
+ 停止数据库：
+
+```shell
+[root@xingdian ~]# systemctl stop mysqld
+```
+
+ 删除数据：
+
+```shell
+[root@xingdian ~]# rm -rf /var/lib/mysql/*
+[root@xingdian ~]# rm -rf /var/log/mysqld.log
+
+其他数据根据实际情况删除
+```
+
+ 依次重演回滚：
+
+```shell
+全备回滚：
+[root@xingdian ~]# innobackupex --apply-log --redo-only /xtrabackup/full/2022-09-25_19-40-47/
+
+第一次增量回滚：
+[root@xingdian ~]# innobackupex --apply-log --redo-only /xtrabackup/full/2022-09-25_19-40-47/ --incremental-dir=/xtrabackup/zeng/2022-09-25_19-56-00/
+
+第二次增量回滚：
+[root@xingdian ~]# innobackupex --apply-log --redo-only /xtrabackup/full/2022-09-25_19-40-47/ --incremental-dir=/xtrabackup/zeng/2022-09-25_19-58-12/
+
+根据实际增量备份的次数回滚，可以想恢复到那个时间节点就回滚到那个时间节点，所有的回滚都给全备
+```
+
+ 恢复数据：
+
+```shell
+[root@xingdian ~]# innobackupex --copy-back /xtrabackup/full/2022-09-25_19-40-47/
+```
+
+ 修改权限：
+
+```shell
+[root@xingdian ~]# chown mysql.mysql /var/lib/mysql -R
+```
+
+ 启动数据库：
+
+```shell
+[root@xingdian ~]# systemctl start mysqld
+```
+
+ 验证：
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 2
+Server version: 5.7.39 MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| mysql |
+| performance_schema |
+| sys |
+| t1 |
+| t2 |
+| t3 |
++--------------------+
+```
+
+##### 差异备份
+
+原理：只备份跟完整备份不一样的
+
+注意：在进行增量备份前先进行完整备份
+
+案例：周一进行全备，周二到周天进行差异备份
+
+ 完整备份：（周一）
+
+```shell
+[root@xingdian ~]# mkdir -p /xtrabackup/full
+[root@xingdian ~]# innobackupex --user=root --password=QianFeng@123 /xtrabackup/full
+```
+
+ 模拟数据增加（略）
+
+ 第一次差异备份：（周二）
+
+```shell
+[root@xingdian ~]# mkdir -p /xtrabackup/jian
+[root@xingdian ~]# innobackupex --user=root --password=QianFeng@123 --incremental /xtrabackup/jian --incremental-basedir=/xtrabackup/full/2022-09-25_20-10-52/
+
+查看第一次差异备份的数据：
+[root@xingdian ~]# ls /xtrabackup/jian/
+2022-09-25_20-12-55
+```
+
+ 模拟数据增加（略）
+
+ 第二次差异备份：（周三）
+
+```shell
+[root@xingdian ~]# innobackupex --user=root --password=QianFeng@123 --incremental /xtrabackup/jian --incremental-basedir=/xtrabackup/full/2022-09-25_20-10-52/
+
+查看第二次差异备份的数据：
+[root@xingdian ~]# ls /xtrabackup/jian/
+2022-09-25_20-12-55 2022-09-25_20-14-32
+
+注意：后面的差异备份跟之前一样，根据需求可以继续差异备份
+```
+
+差异备份恢复流程：（模拟数据丢失）
+
+ 停止数据库：
+
+```shell
+[root@xingdian ~]# systemctl stop mysqld
+```
+
+ 删除数据：
+
+```shell
+[root@xingdian ~]# rm -rf /var/lib/mysql/*
+[root@xingdian ~]# rm -rf /var/log/mysqld.log
+```
+
+ 重演数据回滚：
+
+```shell
+完整备份回滚：
+[root@xingdian ~]# innobackupex --apply-log --redo-only /xtrabackup/full/2022-09-25_20-10-52/
+
+差异备份回滚（根据差异备份的原理，如果恢复所有数据只需要将最后依次差异回滚）
+[root@xingdian ~]# innobackupex --apply-log --redo-only /xtrabackup/full/2022-09-25_20-10-52/ --incremental-dir=/xtrabackup/jian/2022-09-25_20-14-32/
+```
+
+ 恢复数据：
+
+```shell
+[root@xingdian ~]# innobackupex --copy-back /xtrabackup/full/2022-09-25_20-10-52/
+```
+
+ 修改权限：
+
+```shell
+[root@xingdian ~]# chown mysql.mysql /var/lib/mysql -R
+```
+
+ 启动数据库：
+
+```shell
+[root@xingdian ~]# systemctl start mysqld
+```
+
+ 数据验证：
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 2
+Server version: 5.7.39 MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> show databases;
++--------------------+
+| Database |
++--------------------+
+| information_schema |
+| k1 |
+| k2 |
+| mysql |
+| performance_schema |
+| sys |
++--------------------+
+9 rows in set (0.00 sec)
+```
+
+#### 4.mysqldump备份
+
+备份表：（前提有库有表）
+
+```shell
+[root@xingdian ~]# mysqldump -u root -pQianFeng@123 k1 t1 > /t1.sql
+```
+
+恢复表：（恢复之前模拟数据丢失）
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123 k1 < /t1.sql
+mysql: [Warning] Using a password on the command line interface can be insecure.
+```
+
+验证：
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -e "use k1;show tables"
+mysql: [Warning] Using a password on the command line interface can be insecure.
++--------------+
+| Tables_in_k1 |
++--------------+
+| t1 |
++--------------+
+```
+
+备份一个库：
+
+```shell
+[root@xingdian ~]# mysqldump -u root -pQianFeng@123 k1 > /k1.sql
+```
+
+备份多个库：
+
+```shell
+[root@xingdian ~]# mysqldump -u root -pQianFeng@123 -B k1 k2 > /kall.sql
+```
+
+备份所有库：
+
+```shell
+[root@xingdian ~]# mysqldump -u root -pQianFeng@123 -A > /all.sql
+```
+
+数据恢复：
+
+ 为保证数据一致性，应在恢复数据之前停止数据库对外的服务,停止binlog日志
+
+ binlog使用binlog日志恢复数据时也会产生binlog日志（如果开启的话，需要关闭）
+
+```shell
+mysql> set sql_log_bin=0;
+Query OK, 0 rows affected (0.00 sec)
+```
+
+ 模拟数据丢失（略）
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -D k1 < /k1.sql
+mysql: [Warning] Using a password on the command line interface can be insecure.
+ERROR 1049 (42000): Unknown database 'k1'
+出现该错误是因为在恢复的时候需要有库的存在
+
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -e "create database k1"
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -D k1 < /k1.sql
+
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -e "create database k1"
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -e "create database k2"
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -D k1 k2 < /kall.sql
+
+或者
+mysql> source /k1.sql
+```
+
+验证：
+
+```shell
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -e "use k1; show tables;"
+mysql: [Warning] Using a password on the command line interface can be insecure.
++--------------+
+| Tables_in_k1 |
++--------------+
+| t1 |
++--------------+
+[root@xingdian ~]# mysql -u root -pQianFeng@123 -e "use k2; show tables;"
+mysql: [Warning] Using a password on the command line interface can be insecure.
++--------------+
+| Tables_in_k2 |
++--------------+
+| t1 |
++--------------+
+```
+
+#### 5.binlog日志备份
+
+原理：日志方法备份恢复数据
+
+日志默认存储位置：
+
+ rpm ： /var/lib/mysql
+
+ 编译: 安装目录的var下
+
+产生日志：
+
+ 方式一：编译安装
+
+```shell
+[root@xingdian ~]# mysqld_safe --log-bin --user=mysql --server-id=1 &
+
+查看binlog日志
+[root@xingdian ~]# mysqlbinlog slave2-bin.000001 -v --base64-output=decode-rows
+ 时间点 ： 141126 14:04:49
+ 位置点 : at 106
+```
+
+ 方式二：rpm安装（永久）
+
+```shell
+[root@xingdian ~]# vim /etc/my.cnf
+log-bin=mylog
+server-id=1 //做主从复制使用
+
+[root@xingdian ~]# systemctl restart mysqld
+
+查看：
+[root@xingdian ~]# ls /var/lib/mysql
+auto.cnf client-key.pem ib_logfile1 mysql private_key.pem sys
+ca-key.pem ib_buffer_pool ibtmp1 mysql.sock public_key.pem xingdian-bin.index
+ca.pem ibdata1 mylog.000001 mysql.sock.lock server-cert.pem xtrabackup_info
+client-cert.pem ib_logfile0 mylog.index
+
+[root@xingdian ~]# mysqlbinlog /var/lib/mysql/mylog.000001 -v --base64-output=decode-rows
+/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=1*/;
+/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
+DELIMITER /*!*/;
+# at 4
+#220925 21:12:47 server id 1 end_log_pos 123 CRC32 0x52358645 Start: binlog v 4, server v 5.7.39-log created 220925 21:12:47 at startup
+# Warning: this binlog is either in use or was not closed properly.
+ROLLBACK/*!*/;
+# at 123
+#220925 21:12:47 server id 1 end_log_pos 154 CRC32 0xa84d8536 Previous-GTIDs
+# [empty]
+# at 154
+#220925 21:13:38 server id 1 end_log_pos 219 CRC32 0xc2b00431 Anonymous_GTID last_committed=0 sequence_number=1 rbr_only=no
+SET @@SESSION.GTID_NEXT= 'ANONYMOUS'/*!*/;
+# at 219
+#220925 21:13:38 server id 1 end_log_pos 307 CRC32 0x635401a5 Query thread_id=2 exec_time=0 error_code=0
+SET TIMESTAMP=1664111618/*!*/;
+SET @@session.pseudo_thread_id=2/*!*/;
+SET @@session.foreign_key_checks=1, @@session.sql_auto_is_null=0, @@session.unique_checks=1, @@session.autocommit=1/*!*/;
+SET @@session.sql_mode=1436549152/*!*/;
+SET @@session.auto_increment_increment=1, @@session.auto_increment_offset=1/*!*/;
+/*!\C utf8 *//*!*/;
+SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=8/*!*/;
+SET @@session.lc_time_names=0/*!*/;
+SET @@session.collation_database=DEFAULT/*!*/;
+create database t1
+/*!*/;
+SET @@SESSION.GTID_NEXT= 'AUTOMATIC' /* added by mysqlbinlog */ /*!*/;
+DELIMITER ;
+# End of log file
+/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;
+/*!50530 SET @@SESSION.PSEUDO_SLAVE_MODE=0*/;
+
+方法二：
+mysql> show binlog events in "mylog.000001";
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+| Log_name | Pos | Event_type | Server_id | End_log_pos | Info |
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+| mylog.000001 | 4 | Format_desc | 1 | 123 | Server ver: 5.7.39-log, Binlog ver: 4 |
+| mylog.000001 | 123 | Previous_gtids | 1 | 154 | |
+| mylog.000001 | 154 | Anonymous_Gtid | 1 | 219 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' |
+| mylog.000001 | 219 | Query | 1 | 307 | create database t1 |
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+4 rows in set (0.00 sec)
+
+默认查看第一个
+mysql> show binlog events;
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+| Log_name | Pos | Event_type | Server_id | End_log_pos | Info |
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+| mylog.000001 | 4 | Format_desc | 1 | 123 | Server ver: 5.7.39-log, Binlog ver: 4 |
+| mylog.000001 | 123 | Previous_gtids | 1 | 154 | |
+| mylog.000001 | 154 | Anonymous_Gtid | 1 | 219 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' |
+| mylog.000001 | 219 | Query | 1 | 307 | create database t1 |
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+4 rows in set (0.00 sec)
+```
+
+数据恢复：
+
+ 根据时间点恢复数据：
+
+```shell
+[root@xingdian ~]# mysqlbinlog --start-datetime='2022-9-25 21:12:47' --stop-datetime='2022-9-25 21:16:55' /var/lib/mysql/mylog.000001 | mysql -u root -pQianFeng@123
+```
+
+ 根据位置点恢复数据：
+
+```shell
+mysql> show binlog events;
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+| Log_name | Pos | Event_type | Server_id | End_log_pos | Info |
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+| mylog.000001 | 4 | Format_desc | 1 | 123 | Server ver: 5.7.39-log, Binlog ver: 4 |
+| mylog.000001 | 123 | Previous_gtids | 1 | 154 | |
+| mylog.000001 | 154 | Anonymous_Gtid | 1 | 219 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' |
+| mylog.000001 | 219 | Query | 1 | 307 | create database t1 |
+| mylog.000001 | 307 | Anonymous_Gtid | 1 | 372 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' |
+| mylog.000001 | 372 | Query | 1 | 453 | drop database t1 |
+| mylog.000001 | 453 | Anonymous_Gtid | 1 | 518 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' |
+| mylog.000001 | 518 | Query | 1 | 606 | create database t1 |
+| mylog.000001 | 606 | Anonymous_Gtid | 1 | 671 | SET @@SESSION.GTID_NEXT= 'ANONYMOUS' |
+| mylog.000001 | 671 | Query | 1 | 752 | drop database t1 |
++--------------+-----+----------------+-----------+-------------+---------------------------------------+
+[root@xingdian ~]# mysqlbinlog --start-position 219 --stop-position 307 /var/lib/mysql/mylog.000001 | mysql -u root -pQianFeng@123
+```
\ No newline at end of file
diff --git a/第四章：数据库日志管理.md b/第四章：数据库日志管理.md
new file mode 100644
index 0000000..4388809
--- /dev/null
+++ b/第四章：数据库日志管理.md
@@ -0,0 +1,135 @@
+数据库日志管理
+
+
+
+------
+
+## 一：日志管理
+
+
+
+#### 1.日志分类
+
+ 错误日志 ：启动，停止，关闭失败报错。rpm安装日志位置 /var/log/mysqld.log
+
+ 通用查询日志：所有的查询都记下来
+
+ 二进制日志：实现备份，增量备份。只记录改变数据，除了select都记
+
+ 中继日志：读取主服务器的binlog，在本地回放。保持一致
+
+ slow log：慢查询日志，指导调优，定义某一个查询语句，定义超时时间，通过日志提供调优建议给开发人员
+
+ DDL log： 定义语句的日志
+
+#### 2.Error Log
+
+```shell
+log-error=/var/log/mysqld.log
+```
+
+#### 3.Binary Log
+
+```
+log-bin=/var/log/mysql-bin/slave2
+server-id=2
+
+[root@slave2 ~]# mkdir /var/log/mysql-bin
+[root@slave2 ~]# chown mysql.mysql /var/log/mysql-bin/
+[root@slave2 ~]# systemctl restart mysqld
+```
+
+注意：
+
+ 需要提前开启
+
+查看binlog日志：
+
+```shel
+[root@slave2 ~]# mysqlbinlog slave2-bin.000001 -v --base64-output=decode-rows
+ 时间点 ： 141126 14:04:49
+ 位置点 : at 106
+注：
+1. 重启mysqld 会截断
+2. flush logs 会截断
+3. reset master 删除所有binlog rm -rf /var/lib/mysql/*.000001
+4. 删除部分
+PURGE BINARY LOGS TO 'mysql-bin.010';
+PURGE BINARY LOGS BEFORE '2019-04-02 22:46:26';
+
+截取binlog
+all：
+# mysqlbinlog mysql.000002
+
+datetime：
+# mysqlbinlog mysql.000002 --start-datetime="2018-12-05 10:02:56"
+# mysqlbinlog mysql.000002 --stop-datetime="2018-12-05 11:02:54"
+# mysqlbinlog mysql.000002 --start-datetime="2018-12-05 10:02:56" --stop-datetime="2018-12-05 11:02:54"
+
+position：
+# mysqlbinlog mysql.000002 --start-position=260
+# mysqlbinlog mysql.000002 --stop-position=260
+# mysqlbinlog mysql.000002 --start-position=260 --stop-position=930
+```
+
+#### 4.Slow Query Log
+
+开启慢查询日志：
+
+```shell
+[root@xingdian ~]# vim /etc/my.cnf
+slow_query_log=1
+slow_query_log_file=/var/log/mysql-slow/slow.log
+long_query_time=3 设置慢查询超时时间 单位是：秒
+```
+
+创建对应目录：
+
+```shell
+[root@xingdian ~]# mkdir /var/log/mysql-slow
+[root@xingdian ~]# chown mysql.mysql mysql-slow
+```
+
+重启服务：
+
+```shell
+[root@xingdian ~]# systemctl restart mysqld
+```
+
+验证：
+
+```shell
+[root@xingdian ~]# mysql -uroot -pQianFeng@123
+mysql: [Warning] Using a password on the command line interface can be insecure.
+Welcome to the MySQL monitor. Commands end with ; or \g.
+Your MySQL connection id is 2
+Server version: 5.7.39-log MySQL Community Server (GPL)
+
+Copyright (c) 2000, 2022, Oracle and/or its affiliates.
+
+Oracle is a registered trademark of Oracle Corporation and/or its
+affiliates. Other names may be trademarks of their respective
+owners.
+
+Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
+
+mysql> select sleep(6);
++----------+
+| sleep(6) |
++----------+
+| 0 |
++----------+
+1 row in set (6.00 sec)
+
+mysql> exit
+Bye
+[root@xingdian ~]# cat /var/log/mysql-slow/slow.log
+/usr/sbin/mysqld, Version: 5.7.39-log (MySQL Community Server (GPL)). started with:
+Tcp port: 0 Unix socket: /var/lib/mysql/mysql.sock
+Time Id Command Argument
+# Time: 2022-09-25T06:58:05.496205Z
+# User@Host: root[root] @ localhost [] Id: 2
+# Query_time: 6.007094 Lock_time: 0.000000 Rows_sent: 1 Rows_examined: 0
+SET timestamp=1664089085;
+select sleep(6);
+```