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MySQL之备份与多表查询

• 1. 备份与恢复
• • 1.1 备份单个表格与恢复
  • 1.2 对库进行备份并恢复
• 2. 差异备份与恢复
• • 2.1 完全备份
  • • 2.1.1对库进行修改
    • 2.1.2 模拟误删操作
    • 2.1.3 恢复完全备份
    • 2.2 恢复差异备份
  • 2.3 使用mysqlbinlog命令恢复差异备份
• 3. 多表查询
• • 3.1内连接
  • 3.2 左连接
  • 3.3 右连接

1. 备份与恢复

1.1 备份单个表格与恢复

MariaDB [wzw]> show tables;
+---------------+
| Tables_in_wzw |
+---------------+
| student       |
+---------------+
1 row in set (0.000 sec)
对student表进行备份
[root@node1 opt]# mysqldump -uroot -p wzw student > student-$(date '+%Y%m%d').sql
Enter password: 
[root@node1 opt]# ls
playbook  student-20210826.sql

//  删除表
MariaDB [wzw]> drop table student;
Query OK, 0 rows affected (0.008 sec)

MariaDB [wzw]> show tables;
Empty set (0.000 sec)

// 对表进行恢复
[root@node1 opt]# mysql -uroot -p wzw < student-20210826.sql 
Enter password: 
[root@node1 opt]# 
MariaDB [wzw]> show tables;
+---------------+
| Tables_in_wzw |
+---------------+
| student       |
+---------------+
1 row in set (0.000 sec)

1.2 对库进行备份并恢复

MariaDB [wzw]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
| wzw                |
+--------------------+
5 rows in set (0.000 sec)

[root@node1 opt]# mysqldump -uroot -p --all-databases > all-$(date '+%Y%m%d').sql
Enter password: 
[root@node1 opt]# 

// 对库进行恢复
MariaDB [wzw]> drop database wzw ;
Query OK, 1 row affected (0.005 sec)

MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
+--------------------+
4 rows in set (0.000 sec)

[root@node1 opt]# mysql -uroot -p < all-20210826.sql 
Enter password:
[root@node1 opt]# 
MariaDB [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| test               |
| wzw                |
+--------------------+
5 rows in set (0.001 sec)

2. 差异备份与恢复

2.1 完全备份

[root@node1 mysql]# mysqldump -uroot -p --single-transaction --flush-logs --master-data=2 --all-databases --delete-master-logs > all-2021-08-26.sql
Enter password:
[root@node1 opt]#

[root@node1 mysql]# ls
aria_log.00000001  ibtmp1             mysql_upgrade_info
aria_log_control   multi-master.info  performance_schema
ib_buffer_pool     mysql              test
ibdata1            mysql-bin.000002   wzw
ib_logfile0        mysql-bin.index
ib_logfile1        mysql.sock

2.1.1对库进行修改

MariaDB [wzw]> update student set age=18 where id=10;
Query OK, 1 row affected (0.001 sec)
Rows matched: 1  Changed: 1  Warnings: 0

MariaDB [wzw]> delete from student where name='jerry';
Query OK, 1 row affected (0.001 sec)

MariaDB [wzw]> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangsan    |   26 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   18 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
9 rows in set (0.000 sec)

2.1.2 模拟误删操作

// 删除数据库

MariaDB [wzw]> drop database wzw;
Query OK, 1 row affected (0.003 sec)

// 刷新库的日志文件

[root@node1 ~]# mysqladmin -uroot -p flush-logs
Enter password:
[root@node1 ~]#

[root@node1 mysql]# ls
aria_log.00000001  ibtmp1             mysql.sock
aria_log_control   multi-master.info  mysql_upgrade_info
ib_buffer_pool     mysql              performance_schema
ibdata1            mysql-bin.000002   test
ib_logfile0        mysql-bin.000003
ib_logfile1        mysql-bin.index

2.1.3 恢复完全备份

[root@node1 opt]# mysql -uroot -p < all-2021-08-26.sql 
Enter password:
[root@node1 opt]#

MariaDB [wzw]> select  * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  2 | jerry       |   23 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangsan    |   26 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   15 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
10 rows in set (0.000 sec)

2.2 恢复差异备份

// 先查看误删数据库所在的位置

MariaDB [wzw]> show binlog events in 'mysql-bin.000002';
+------------------+-----+-------------------+-----------+-------------+---------------------------------------------------+
| Log_name         | Pos | Event_type        | Server_id | End_log_pos | Info                                              |
+------------------+-----+-------------------+-----------+-------------+---------------------------------------------------+
| mysql-bin.000002 |   4 | Format_desc       |         1 |         256 | Server ver: 10.3.17-MariaDB-log, Binlog ver: 4    |
| mysql-bin.000002 | 256 | Gtid_list         |         1 |         285 | []                                                |
| mysql-bin.000002 | 285 | Binlog_checkpoint |         1 |         328 | mysql-bin.000001                                  |
| mysql-bin.000002 | 328 | Binlog_checkpoint |         1 |         371 | mysql-bin.000002                                  |
| mysql-bin.000002 | 371 | Gtid              |         1 |         413 | BEGIN GTID 0-1-1                                  |
| mysql-bin.000002 | 413 | Query             |         1 |         517 | use `wzw`; delete from student where name='jerry' |
| mysql-bin.000002 | 517 | Xid               |         1 |         548 | COMMIT /* xid=437 */                              |
| mysql-bin.000002 | 548 | Gtid              |         1 |         590 | BEGIN GTID 0-1-2                                  |
| mysql-bin.000002 | 590 | Query             |         1 |         693 | use `wzw`; update student set age=18 where id=10  |
| mysql-bin.000002 | 693 | Xid               |         1 |         724 | COMMIT /* xid=439 */                              |
| mysql-bin.000002 | 724 | Gtid              |         1 |         766 | GTID 0-1-3                                        |
| mysql-bin.000002 | 766 | Query             |         1 |         849 | drop database wzw                                 |
| mysql-bin.000002 | 849 | Rotate            |         1 |         896 | mysql-bin.000003;pos=4                            |
+------------------+-----+-------------------+-----------+-------------+---------------------------------------------------+
13 rows in set (0.001 sec)

2.3 使用mysqlbinlog命令恢复差异备份

这里的766是你开始删除库之前的修改过数据的位置。
mysqlbinlog --stop-position=766 /var/lib/mysql/mysql-bin.000002 | mysql -uroot -p

MariaDB [wzw]> select * from student;
+----+-------------+------+
| id | name        | age  |
+----+-------------+------+
|  1 | tom         |   20 |
|  3 | wangqing    |   25 |
|  4 | sean        |   28 |
|  5 | zhangsan    |   26 |
|  7 | lisi        |   50 |
|  8 | chenshuo    |   10 |
|  9 | wangwu      |  100 |
| 10 | qiuyi       |   18 |
| 11 | qiuxiaotian |   20 |
+----+-------------+------+
9 rows in set (0.000 sec)

3. 多表查询

MariaDB [test]> create table xx (a varchar(20),b varchar(20),c varchar(20));
Query OK, 0 rows affected (0.004 sec)

MariaDB [test]> desc xx;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| a     | varchar(20) | YES  |     | NULL    |       |
| b     | varchar(20) | YES  |     | NULL    |       |
| c     | varchar(20) | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
3 rows in set (0.001 sec)

MariaDB [test]> select * from xx;
+------+------+------+
| a    | b    | c    |
+------+------+------+
| 1    | a    | ss   |
| 1    | a    | ss   |
| 1    | a    | ss   |
| 1    | a    | ss   |
| 1    | a    | ss   |
| 1    | b    | qq   |
| 1    | b    | qq   |
| 1    | b    | qq   |
| 1    | b    | qq   |
+------+------+------+
9 rows in set (0.000 sec)

以b列来进行分组(count groupby 的应用)
统计b这一列中a和b出现的次数

MariaDB [test]> select count(a),b from xx group by b;
+----------+------+
| count(a) | b    |
+----------+------+
|        5 | a    |
|        4 | b    |
+----------+------+
2 rows in set (0.001 sec)
统计c这一列中qq和ss出现的次数
MariaDB [test]> select count(a),c from xx group by c;
+----------+------+
| count(a) | c    |
+----------+------+
|        4 | qq   |
|        5 | ss   |
+----------+------+
2 rows in set (0.001 sec)

统计xx这个表中c这一列qq和ss出现的次数
MariaDB [test]> select c,count(c) from xx group by c;   //括号里的c可以是这个表里的其他数字或字母
+------+----------+
| c    | count(c) |
+------+----------+
| qq   |        4 |
| ss   |        5 |
+------+----------+
2 rows in set (0.000 sec)

求age这一列的平均值
MariaDB [wzw]> select avg(age) from student;
+----------+
| avg(age) |
+----------+
|  33.0000 |
+----------+
1 row in set (0.000 sec)

求age这一列的和
MariaDB [wzw]> select sum(age) from student;
+----------+
| sum(age) |
+----------+
|      297 |
+----------+
1 row in set (0.000 sec)

3.1内连接

意思是a表和b的表的内连接中a的id和b的parent_id相等的有哪些

MariaDB [test]> select a.*,b.* from a inner join b on a.id=b.parent_id;
+------+----------+------+------+-----------+
| id   | name     | id   | job  | parent_id |
+------+----------+------+------+-----------+
|    1 | zhangsan |    1 |   23 |         1 |
|    2 | lisi     |    2 |   34 |         2 |
+------+----------+------+------+-----------+
2 rows in set (0.001 sec)

3.2 左连接

意思是a表和b的表的左连接中以a表为标准进行比较，显示b表与a表的相同和不同的地方有哪些

MariaDB [test]> select a.*,b.* from a left join b on a.id=b.parent_id;
+------+----------+------+------+-----------+
| id   | name     | id   | job  | parent_id |
+------+----------+------+------+-----------+
|    1 | zhangsan |    1 |   23 |         1 |
|    2 | lisi     |    2 |   34 |         2 |
|    3 | wangwu   | NULL | NULL |      NULL |
+------+----------+------+------+-----------+

3.3 右连接

意思是a表和b的表的左连接中以b表为标准进行比较，显示b表与a表的相同和不同的地方有哪些

MariaDB [test]> select a.*,b.* from a right join b on a.id=b.parent_id;
+------+----------+------+------+-----------+
| id   | name     | id   | job  | parent_id |
+------+----------+------+------+-----------+
|    1 | zhangsan |    1 |   23 |         1 |
|    2 | lisi     |    2 |   34 |         2 |
| NULL | NULL     |    3 |   34 |         4 |
+------+----------+------+------+-----------+
3 rows in set (0.000 sec)

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