一、逻辑备份
逻辑备份：备份的是建表，建库，插入数据等操作所执行SQL语句，适用于中小型数据库，效率相对较低，提供三种级别的备份，表级，库级和全库级。
**本质：**导出的是SQL语句
**优点：**不论是什么存储引擎，都可以用mysqldump备份成SQL语句
**缺点：**速度较慢，导出时可能会出现格式不兼容的突发状况，无法做增量备份和累计增量备份
数据一致，服务可用:如何保证数据一致，在备份的时候进行锁表会自动锁表。锁住之后在备份。
二、逻辑备份：
1、备份全部数据库
语法：mysqldump -u指定用户 -p指定密码 -A > 文件名
mysqldump -u指定用户 -p指定密码 --all-databases > 文件名
[root@localhost ~]# mysqldump -uroot -p123 -A > all.mysql
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# mysqldump -uroot -p123 --all-database >all1.txt
mysqldump: [Warning] Using a password on the command line interface can be insecure.2.备份部分数据库
语法：mysqldump -u指定用户 -p密码 -B 数据库名1 数据库名2> 文件名
mysqldump -u指定用户 -p密码 --databases 数据库名1 数据库名2 > 文件名
[root@localhost ~]# mysqldump -uroot -p123 -B db1 >db1.txt
mysqldump: [Warning] Using a password on the command line interface can be insecure.
[root@localhost ~]# mysqldump -uroot -p123 --databases db1 school > db2.txt
mysqldump: [Warning] Using a password on the command line interface can be insecure.3.备份表
语法：mysqldump -u指定用户 -p指定密码 数据库名 表名 > 文件名
[root@localhost ~]# mysqldump -uroot -p123 db1 employee > employee.txt
mysqldump: [Warning] Using a password on the command line interface can be insecure.4.备份表结构
语法：mysqldump -u指定用户 -p指定密码 -d 数据库名 表名
[root@localhost ~]# mysqldump -uroot -p123 -d db1 employee > jiegou.txt
mysqldump: [Warning] Using a password on the command line interface can be insecure.5.备份表数据
语法：select * from 表.库 into outfile'/var/lib/mysql-files/文件名'；
mysql> show variables like 'secure%'; #查看默认导出路径
+------------------+-----------------------+
| Variable_name | Value |
+------------------+-----------------------+
| secure_auth | ON |
| secure_file_priv | /var/lib/mysql-files/ |
+------------------+-----------------------+
2 rows in set (0.00 sec)
mysql> select * from mysql.user into outfile '/var/lib/mysql-files/b.xfs';
Query OK, 6 rows affected (0.00 sec)扩展：修改默认的导出路径
[root@localhost opt]# mkdir backup #创建默认目录
[root@localhost opt]# chown -R mysql.mysql /opt/backup#修改目录的属主和属组
[root@localhost opt]# vim /etc/my.cnf #修改配置文件
secure_file_priv=/opt/backup
[root@localhost opt]# systemctl restart mysqld #重启mysql
[root@localhost opt]# mysql -p123 #进入mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.7.43 MySQL Community Server (GPL)
Copyright (c) 2000, 2023, 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 variables like 'secure%'; #再次查看文件的默认路径
+------------------+--------------+
| Variable_name | Value |
+------------------+--------------+
| secure_auth | ON |
| secure_file_priv | /opt/backup/ |
+------------------+--------------+
2 rows in set (0.01 sec)6.恢复
（1）命令行恢复数据库
a)命令行恢复
语法：mysql -u用户名 -p密码 < 之前备份的文件
mysql> drop database db1; #先删除数据库db1
Query OK, 15 rows affected (0.07 sec)
mysql> show databases; #查看数据库
+--------------------+
| Database |
+--------------------+
| information_schema |
| db3 |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
6 rows in set (0.00 sec)
[root@localhost ~]# mysql -uroot -p123 < db1.txt #恢复数据库
mysql: [Warning] Using a password on the command line interface can be insecure.
mysql> show databases; #再次查看数据库
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| db3 |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
7 rows in set (0.00 sec)b)数据库里面恢复
语法：source +备份数据库的路径
mysql> drop database db1; #删除数据库db1
Query OK, 15 rows affected (0.05 sec)
mysql> source /root/db1.txt #恢复数据库db1
Query OK, 0 rows affected (0.00 sec)
.
.
Query OK, 0 rows affected (0.00 sec)
mysql> show databases; #查看数据库
+--------------------+
| Database |
+--------------------+
| information_schema |
| db1 |
| db3 |
| mysql |
| performance_schema |
| school |
| sys |
+--------------------+
7 rows in set (0.00 sec)（2）恢复表
a)在命令行恢复
语法：mysql -u用户 -p密码 表所在的数据库< 备份的文件
[root@localhost ~]# mysql -uroot -p123 db1< employee.txt
mysql: [Warning] Using a password on the command line interface can be insecure.b)在数据库里面恢复
语法：source +备份的路径
mysql> source /root/employee.txt
Query OK, 0 rows affected (0.00 sec)
Query OK, 0 rows affected (0.00 sec)（3）恢复表结构
语法：mysql -u用户 -p密码 -D 数据库名 < 备份的文件
[root@localhost ~]# mysql -uroot -p123 -D db1 <jiegou.txt
mysql: [Warning] Using a password on the command line interface can be insecure.
mysql> desc employee;
+-----------------+---------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+---------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(30) | NO | | NULL | |
| sex | enum('man','woman') | YES | | man | |
| hire_date | date | YES | | NULL | |
| post | varchar(20) | YES | | NULL | |
| job_description | varchar(100) | YES | | NULL | |
| salary | double(15,2) | NO | | NULL | |
| office | int(11) | YES | | NULL | |
| dep_id | int(11) | YES | | NULL | |
+-----------------+---------------------+------+-----+---------+----------------+
9 rows in set (0.00 sec)
mysql> select * from employee;
Empty set (0.00 sec)（4）恢复表中数据
mysql> truncate employee;
Query OK, 0 rows affected (0.02 sec)
mysql> select * from employee;
Empty set (0.00 sec)
mysql> load data infile'/opt/backup/a.txt'into table employee;
Query OK, 15 rows affected (0.01 sec)
Records: 15 Deleted: 0 Skipped: 0 Warnings: 0
mysql> select * from employee;
+----+-----------+-------+------------+------------+-----------------+----------+--------+--------+
| id | name | sex | hire_date | post | job_description | salary | office | dep_id |
+----+-----------+-------+------------+------------+-----------------+----------+--------+--------+
| 1 | qiancheng | man | 2018-03-14 | hr | talk | 7000.00 | 501 | 102 |
| 20 | tom | man | 2017-09-15 | instructor | teach | 8000.00 | 501 | 100 |
| 21 | alince | woman | 2013-04-28 | instructor | teach | 5500.00 | 501 | 100 |
| 22 | robin | man | 2020-09-18 | instructor | teach | 7200.00 | 501 | 100 |
| 23 | zhuzhu | man | 2016-12-09 | hr | hrcc | 6000.00 | 502 | 101 |
| 24 | gougou | woman | 2015-04-27 | hr | NULL | 6000.00 | 502 | 101 |
| 30 | maomao | man | 2019-08-12 | sale | talk | 20000.00 | 503 | 102 |
| 31 | yiyi | man | 2015-06-17 | talk | NULL | 8000.00 | NULL | NULL |
| 40 | harry | woman | 2018-02-05 | hr | hrcc | 6900.00 | 502 | 102 |
| 41 | tianyuan | man | 2018-02-05 | null | salecc | 9700.00 | 501 | 102 |
| 42 | xiaoyi | man | 2018-02-05 | null | salecc | 5700.00 | 501 | 102 |
| 50 | zxvb | man | 2019-04-23 | hr | NULL | 8000.00 | NULL | NULL |
| 51 | ab | man | NULL | NULL | NULL | 6500.00 | NULL | NULL |
| 52 | cd | man | NULL | NULL | NULL | 7600.00 | NULL | NULL |
| 53 | ef | man | NULL | NULL | NULL | 8900.00 | NULL | NULL |
+----+-----------+-------+------------+------------+-----------------+----------+--------+--------+
15 rows in set (0.00 sec)