原来自己用的是为了装的， 所以在设置database usage（如下图1）的时候按照discuz官方的建议，选的都是Non-Transactional Database Only（只支持MyISAM数据引擎的非事务数据库），用MyISAM数据库，还没涉及到需要InnoDB，因此打算直接不加载INNODB引擎。
后来在做WordPress，一开始还不知道原来WordPress用的是InnoDB数据引擎，于是在原来的数据库里面就建了一个数据库,一开始也没发觉问题，安装，导入sql，都没问题，当时也没多想。直到这几天因为又要装多一个WordPress，用phpmyadmin访问数据库多一点，问题来了。老是一访问WordPress的数据库，就弹出错误提示“图1 设置数据库类型
纠结了挺久，也忘了是看到什么文章触发了灵感，反正后来才知道原来是数据引擎不同惹的祸。于是就想到重新运行次设置向导，把数据库类型改成支持InnoDB引擎的。马上行动，在向导里设置数据库类型（也就是图1的database usage）那里，设置成第二项，还在后面的InnoDB Tablespace Settings里把InnoDB数据文件设置放在D:\MySQL InnoDB Datafiles目录里。但是在最后execute执行的时候，却老是在Start Service那里出问题，如下图2。
图2 Start service出错 想直接到services.msc里面启动服务，也不行。错误提示“” 按照网上的某些做法，卸载了MySQL服务，也没重启就重新设置，问题如故；把服务卸载了，重启后再重新设置，则是启动服务成功，但是在后面的Applying Security Settings的时候有新的问题，如下图3。图2那里的错误提示则变成“ 图3 顺便提一下，在MySQL5里（其他版本的我不知道）每运行一次设置向导，只要按了execute执行，都会在MySQL5的安装目录下自动生成一个原来的MySQL的设置文件my.ini的备份bak文件。并且将以修改的时间命名。因此如果设置出了问题，可以从备份文件恢复。后来还是在错误日志里找到思路。错误日志就是放在 MySQL5安装目录\Data 目录里的那个以你的计算机名命名的.err文件。 首先我找到以下一段： InnoDB: Error: log file .\ib_logfile0 is of different size 0 52428800 bytes InnoDB: than specified in the .cnf file 0 10485760 bytes! 101001 9:47:42 [ERROR] Default storage engine (InnoDB) is not available 101001 9:47:42 [ERROR] Aborting
101001 9:47:42 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete
于是就到“MySQL5安装目录\Data ”目录里把ib_logfile0日志文件删掉，重启MySQL服务，还是提示10067错误。再去查看err文件。 101001 18:39:29 InnoDB: Log file .\ib_logfile0 did not exist: new to be created InnoDB: Setting log file .\ib_logfile0 size to 109 MB InnoDB: Database physically writes the file full: wait... InnoDB: Progress in MB: 100 InnoDB: Error: log file .\ib_logfile1 is of different size 0 52428800 bytes InnoDB: than specified in the .cnf file 0 114294784 bytes! 101001 18:39:30 [ERROR] Default storage engine (InnoDB) is not available 101001 18:39:30 [ERROR] Aborting
101001 18:39:30 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete
可以看到，ib_logfile0的问题解决了，但是同样的问题却出在ib_logfile1上面了。于是依样画葫芦，把ib_logfile1删了，再重启MySQL服务，却发现没用。难道是还要重启系统。果真，把前面两个ib_logfile删了，重启系统就搞定了。前面的可能是因为刚开机，所以也行。实际上是需要重启系统的。这时的日志如下 101001 19:19:24 InnoDB: Log file .\ib_logfile0 did not exist: new to be created InnoDB: Setting log file .\ib_logfile0 size to 109 MB InnoDB: Database physically writes the file full: wait... InnoDB: Progress in MB: 100 101001 19:19:26 InnoDB: Log file .\ib_logfile1 did not exist: new to be created InnoDB: Setting log file .\ib_logfile1 size to 109 MB InnoDB: Database physically writes the file full: wait... InnoDB: Progress in MB: 100 InnoDB: Cannot initialize created log files because InnoDB: data files are corrupt, or new data files were InnoDB: created when the database was started previous InnoDB: time but the database was not shut down InnoDB: normally after that. 101001 19:19:27 [ERROR] Default storage engine (InnoDB) is not available 101001 19:19:27 [ERROR] Aborting
101001 19:19:27 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete
好了，现在只剩下最后一个问题了Default storage engine (InnoDB) is not available。去services.msc里面启动MySQL服务，还是出错。但是日志却是显示 InnoDB: No valid checkpoint found. InnoDB: If this error appears when you are creating an InnoDB database, InnoDB: the problem may be that during an earlier attempt you managed InnoDB: to create the InnoDB data files, but log file creation failed. InnoDB: If that is the case, please refer to InnoDB: http://dev.mysql.com/doc/mysql/en/Error_creating_InnoDB.html 101001 20:45:09 [ERROR] Default storage engine (InnoDB) is not available 101001 20:45:09 [ERROR] Aborting
101001 20:45:09 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete
于是去网上搜索了一下，发现提示No valid checkpoint found.的
What are the different storage engines available in MySQL?Apr 26, 2025 am 12:27 AMMySQLoffersvariousstorageengines,eachsuitedfordifferentusecases:1)InnoDBisidealforapplicationsneedingACIDcomplianceandhighconcurrency,supportingtransactionsandforeignkeys.2)MyISAMisbestforread-heavyworkloads,lackingtransactionsupport.3)Memoryengineis
What are some common security vulnerabilities in MySQL?Apr 26, 2025 am 12:27 AMCommon security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.
How can you identify slow queries in MySQL?Apr 26, 2025 am 12:15 AMIdentifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.
How can you monitor MySQL server health and performance?Apr 26, 2025 am 12:15 AMTo monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.
Compare and contrast MySQL and MariaDB.Apr 26, 2025 am 12:08 AMThe main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.
How does MySQL's licensing compare to other database systems?Apr 25, 2025 am 12:26 AMMySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.
When would you choose InnoDB over MyISAM, and vice versa?Apr 25, 2025 am 12:22 AMThe situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.
Explain the purpose of foreign keys in MySQL.Apr 25, 2025 am 12:17 AMIn MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.
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