怎么安装mysql数据库,这里不说了,只说它的主从复制,步骤如下 在进行主从设置之前 首先确保mysql主从服务器之间的数据库端口防火墙互相打开, 尽量确保主从数据库账户一致性(主从切换使用),否则将操作失败, 其次是确保mysql账户对mysql数据库目录有“可
怎么安装mysql数据库,这里不说了,只说它的主从复制,步骤如下
在进行主从设置之前
首先确保mysql主从服务器之间的数据库端口防火墙互相打开,
尽量确保主从数据库账户一致性(主从切换使用),否则将操作失败,
其次是确保mysql账户对mysql数据库目录有“可读写”权限非“可写”权限,
为了确保不出意外,最好删除mysql之前陈旧的mysql-bin、mysql日志,然后重启mysql
在主服务器上新建一个new_test数据库并为其建一个test表,然后导出导入到从服务器上(测试主从使用)服务器上可替换成现有的数据库进行操作(我这里主从上各建立一个相同账户和密码,相同的端口配置,为了主从切换,方便测试,记得防火墙端口和日志位置读写权限一定要有的)
1、主从服务器分别作以下操作:
1.1、版本一致
1.2、初始化表,并在后台启动mysql
1.3、修改root的密码
2、修改主服务器master:
#vi /etc/my.cnf
[mysqld]
log-bin=mysql-bin //[必须]启用二进制日志
server-id=1 //[必须]默认是1,一般取IP最后一段
port=1223
bing-address=0.0.0.0
log-bin=mysql-bin.log(必须,数据库日志文件,主从必须)
binlog-do-db =new_test (要记录的数据库,多个可换行多次设置)
replicate-do-db =new_test (要复制的数据库,多个可换行过个设置)
binlog-ignore-db=mysql //不对mysql库进行日志记录操作 如下意思雷同
binlog-ignore-db=test
binlog-ignore-db=information_schema
binlog-ignore-db=performance_schema
replicate-ignore-db=test //不对test进行复制操作 如下意思雷同
replicate-ignore-db=mysql
replicate-ignore-db=information_schema
replicate-ignore-db=performance_schema
3、修改从服务器slave:
#vi /etc/my.cnf
[mysqld]
port=1223
bing-address=0.0.0.0 //意思是允许所有 机器 服务器安全起见可设置为指定的服务器IP地址 如 116.128.1.10等
log-bin=mysql-bin.log
server-id=2
binlog-do-db =new_test
replicate-do-db =new_test
binlog-ignore-db=mysql
binlog-ignore-db=test
binlog-ignore-db=information_schema
binlog-ignore-db=performance_schema
replicate-ignore-db=test
replicate-ignore-db=mysql
replicate-ignore-db=information_schema
replicate-ignore-db=performance_schema
4、重启两台服务器的mysql
service mysql restart
5、在主服务器上建立帐户并授权slave:
#/usr/local/mysql/bin/mysql -u数据库账户名 -p数据库密码
mysql>GRANT REPLICATION SLAVE ON *.* to 'newback_username'@'%' identified by 'newback_pwd'; //一般不用root帐号,“%”表示所有客户端都可能连(安全起见可将%替换成指定服务器IP,如116.121.1.10),只要帐号,密码正确。
6、登录主服务器的mysql,查询master的状态(可在phpmyadmin 中执行次操作)
mysql>show master status;
+------------------+----------+--------------+------------------+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+------------------+----------+--------------+------------------+
| mysql-bin.000001 | 120 | | |
+------------------+----------+--------------+------------------+
1 row in set (0.00 sec)
注:执行完此步骤后不要再操作主服务器MYSQL,防止主服务器状态值变化
7、配置从服务器Slave:
mysql>change master to master_host='116.121.1.10',master_port=1223,master_user='newback',master_password='cctv@12315#$',master_log_file='mysql-bin.000001',master_log_pos=120 //注意不要断开,master_port为mysql服务器端口号(无引号),master_user为执行同步操作的数据库账户,“120”无单引号(此处的120就是show
master status 中看到的position的值,这里的mysql-bin.000001就是file对应的值)。(此处可在从服务器phpmyadmin中用sql语句操作)
Mysql>start slave; //启动从服务器复制功能(可在phpmyadmin中执行该SQL语句)
8、检查从服务器复制功能状态:
mysql> show slave status\G (可在从服务器phpmyadmin中执行“show slave status” SQL语句)
*************************** 1. row ***************************
……………………(省略部分)
Slave_IO_Running: Yes //此状态必须YES
Slave_SQL_Running: Yes //此状态必须YES
……………………(省略部分)
注:Slave_IO及Slave_SQL进程必须正常运行,即YES状态,否则都是错误的状态(如:其中一个NO均属错误)。
以上操作过程,主从服务器配置完成。
9、主从服务器测试:
在主服务器new_test数据库中的test表中插入 或者更新一条记录,如果从服务器同样更新 插入 则配置正确,否则错误
10、mysql5.5+版本与mysql5.5之前版本的一些差异:
其中大部分的内容相似
主要是5.5之后不再支持master打头的参数
如:
master-host,master-user,master-password,master-port等。
错误如下:
[ERROR] /usr/local/mysql/bin/mysqld: unknown variable 'master-host=192.168.2.182'
主配置不变,依旧是
server-id=1
log-bin=log
binlog-do-db=database1
binlog-do-db=database2
binlog-ignore-db=mysql
…………(省略部分)
从配置改为(注意下列注释部分,统统被废弃了):
server-id=2
#master-host=192.168.124.51
#master-user= AffairLog
#master-password= password
#master-port=3306
#master-connect-retry=60
replicate-do-db=database1
replicate-do-db=database2
replicate-ignore-db=mysql
我们需要使用change master to
即:
mysql>change master to
>master_host='192.168.124.51',
>master_user='username',
>master_password='password',
>master_log_file='bin-log.000001',
>master_log_pos=120;
然后start slave;
(也可一句话执行如:"change master to master_host='116.121.1.10',master_port=1223,master_user='newback',master_password='cctv@12315#$',master_log_file='mysql-bin.000001',master_log_pos=120" 【实际命令去掉外面的双引号,端口号和master_log_pos不加引号】 )
其他一切不变
InnoDB uses redologs and undologs to ensure data consistency and reliability. 1.redologs record data page modification to ensure crash recovery and transaction persistence. 2.undologs records the original data value and supports transaction rollback and MVCC.

Key metrics for EXPLAIN commands include type, key, rows, and Extra. 1) The type reflects the access type of the query. The higher the value, the higher the efficiency, such as const is better than ALL. 2) The key displays the index used, and NULL indicates no index. 3) rows estimates the number of scanned rows, affecting query performance. 4) Extra provides additional information, such as Usingfilesort prompts that it needs to be optimized.

Usingtemporary indicates that the need to create temporary tables in MySQL queries, which are commonly found in ORDERBY using DISTINCT, GROUPBY, or non-indexed columns. You can avoid the occurrence of indexes and rewrite queries and improve query performance. Specifically, when Usingtemporary appears in EXPLAIN output, it means that MySQL needs to create temporary tables to handle queries. This usually occurs when: 1) deduplication or grouping when using DISTINCT or GROUPBY; 2) sort when ORDERBY contains non-index columns; 3) use complex subquery or join operations. Optimization methods include: 1) ORDERBY and GROUPB

MySQL/InnoDB supports four transaction isolation levels: ReadUncommitted, ReadCommitted, RepeatableRead and Serializable. 1.ReadUncommitted allows reading of uncommitted data, which may cause dirty reading. 2. ReadCommitted avoids dirty reading, but non-repeatable reading may occur. 3.RepeatableRead is the default level, avoiding dirty reading and non-repeatable reading, but phantom reading may occur. 4. Serializable avoids all concurrency problems but reduces concurrency. Choosing the appropriate isolation level requires balancing data consistency and performance requirements.

MySQL is suitable for web applications and content management systems and is popular for its open source, high performance and ease of use. 1) Compared with PostgreSQL, MySQL performs better in simple queries and high concurrent read operations. 2) Compared with Oracle, MySQL is more popular among small and medium-sized enterprises because of its open source and low cost. 3) Compared with Microsoft SQL Server, MySQL is more suitable for cross-platform applications. 4) Unlike MongoDB, MySQL is more suitable for structured data and transaction processing.

MySQL index cardinality has a significant impact on query performance: 1. High cardinality index can more effectively narrow the data range and improve query efficiency; 2. Low cardinality index may lead to full table scanning and reduce query performance; 3. In joint index, high cardinality sequences should be placed in front to optimize query.

The MySQL learning path includes basic knowledge, core concepts, usage examples, and optimization techniques. 1) Understand basic concepts such as tables, rows, columns, and SQL queries. 2) Learn the definition, working principles and advantages of MySQL. 3) Master basic CRUD operations and advanced usage, such as indexes and stored procedures. 4) Familiar with common error debugging and performance optimization suggestions, such as rational use of indexes and optimization queries. Through these steps, you will have a full grasp of the use and optimization of MySQL.

MySQL's real-world applications include basic database design and complex query optimization. 1) Basic usage: used to store and manage user data, such as inserting, querying, updating and deleting user information. 2) Advanced usage: Handle complex business logic, such as order and inventory management of e-commerce platforms. 3) Performance optimization: Improve performance by rationally using indexes, partition tables and query caches.


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