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
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)