由于项目需要不得不折腾MySQL,RedHatLinux上安装了最新的MySQL 5.6启动报错如下:
[root@tserver mysql]# /etc/init.d/mysql start
Starting MySQL.The server quit without updating PID file (/var/lib/mysql/tserver.pid).[FAILED]
检查报错信息tserver.err。
cat tserver.err
140121 06:03:29 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
2014-01-21 06:03:29 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2014-01-21 06:03:29 14964 [Note] Plugin 'FEDERATED' is disabled.
2014-01-21 06:03:29 14964 [Note] InnoDB: The InnoDB memory heap is disabled
2014-01-21 06:03:29 14964 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2014-01-21 06:03:29 14964 [Note] InnoDB: Compressed tables use zlib 1.2.3
2014-01-21 06:03:29 14964 [Note] InnoDB: Using Linux native AIO
2014-01-21 06:03:29 14964 [Note] InnoDB: Using CPU crc32 instructions
2014-01-21 06:03:29 14964 [Note] InnoDB: Initializing buffer pool, size = 128.0M
2014-01-21 06:03:29 14964 [Note] InnoDB: Completed initialization of buffer pool
2014-01-21 06:03:29 14964 [ERROR] InnoDB: auto-extending data file ./ibdata1 is of a different size 640 pages (rounded down to MB) than specified in the .cnf file: initial 768 pages, max 0 (relevant if non-zero) pages!
2014-01-21 06:03:29 14964 [ERROR] InnoDB: Could not open or create the system tablespace. If you tried to add new data files to the system tablespace, and it failed here, you should now edit innodb_data_file_path in my.cnf back to what it was, and remove the new ibdata files InnoDB created in this failed attempt. InnoDB only wrote those files full of zeros, but did not yet use them in any way. But be careful: do not remove old data files which contain your precious data!
2014-01-21 06:03:29 14964 [ERROR] Plugin 'InnoDB' init function returned error.
2014-01-21 06:03:29 14964 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2014-01-21 06:03:29 14964 [ERROR] Unknown/unsupported storage engine: InnoDB
2014-01-21 06:03:29 14964 [ERROR] Aborting
2014-01-21 06:03:29 14964 [Note] Binlog end
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'partition'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_DATAFILES'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_TABLESPACES'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_FOREIGN_COLS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_FOREIGN'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_FIELDS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_COLUMNS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_INDEXES'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_TABLESTATS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_SYS_TABLES'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_FT_INDEX_TABLE'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_FT_INDEX_CACHE'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_FT_CONFIG'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_FT_BEING_DELETED'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_FT_DELETED'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_FT_DEFAULT_STOPWORD'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_METRICS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_BUFFER_POOL_STATS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_BUFFER_PAGE_LRU'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_BUFFER_PAGE'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_CMP_PER_INDEX_RESET'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_CMP_PER_INDEX'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_CMPMEM_RESET'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_CMPMEM'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_CMP_RESET'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_CMP'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_LOCK_WAITS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_LOCKS'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'INNODB_TRX'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'PERFORMANCE_SCHEMA'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'BLACKHOLE'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'ARCHIVE'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'CSV'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'MEMORY'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'MRG_MYISAM'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'MyISAM'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'sha256_password'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'mysql_old_password'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'mysql_native_password'
2014-01-21 06:03:29 14964 [Note] Shutting down plugin 'binlog'
2014-01-21 06:03:29 14964 [Note] /usr/sbin/mysqld: Shutdown complete
检查发现mysql的目录下有如下文件:
[root@tserver mysql]# ls
ibdata1 ib_logfile0 ib_logfile1 mysql RPM_UPGRADE_HISTORY RPM_UPGRADE_MARKER-LAST test tserver.err
删除了如下三个文件:
[root@tserver mysql]# rm ibdata1 ib_logfile0 ib_logfile1
rm: remove regular file `ibdata1'? yes
rm: remove regular file `ib_logfile0'? yes
rm: remove regular file `ib_logfile1'? yes
重新启动mysql server就可以了:
[root@tserver mysql]# /etc/init.d/mysql start
Starting MySQL.[ OK ]
[root@tserver mysql]# ps -ef|grep mysql
root 15166 1 0 06:12 pts/0 00:00:00 /bin/sh /usr/bin/mysqld_safe --datadir=/var/lib/mysql --pid-file=/var/lib/mysql/tserver.pid
mysql 15257 15166 9 06:12 pts/0 00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/tserver.err --pid-file=/var/lib/mysql/tserver.pid
root 15284 14224 0 06:12 pts/0 00:00:00 grep mysql

MySQL is an open source relational database management system, mainly used to store and retrieve data quickly and reliably. Its working principle includes client requests, query resolution, execution of queries and return results. Examples of usage include creating tables, inserting and querying data, and advanced features such as JOIN operations. Common errors involve SQL syntax, data types, and permissions, and optimization suggestions include the use of indexes, optimized queries, and partitioning of tables.

MySQL is an open source relational database management system suitable for data storage, management, query and security. 1. It supports a variety of operating systems and is widely used in Web applications and other fields. 2. Through the client-server architecture and different storage engines, MySQL processes data efficiently. 3. Basic usage includes creating databases and tables, inserting, querying and updating data. 4. Advanced usage involves complex queries and stored procedures. 5. Common errors can be debugged through the EXPLAIN statement. 6. Performance optimization includes the rational use of indexes and optimized query statements.

MySQL is chosen for its performance, reliability, ease of use, and community support. 1.MySQL provides efficient data storage and retrieval functions, supporting multiple data types and advanced query operations. 2. Adopt client-server architecture and multiple storage engines to support transaction and query optimization. 3. Easy to use, supports a variety of operating systems and programming languages. 4. Have strong community support and provide rich resources and solutions.

InnoDB's lock mechanisms include shared locks, exclusive locks, intention locks, record locks, gap locks and next key locks. 1. Shared lock allows transactions to read data without preventing other transactions from reading. 2. Exclusive lock prevents other transactions from reading and modifying data. 3. Intention lock optimizes lock efficiency. 4. Record lock lock index record. 5. Gap lock locks index recording gap. 6. The next key lock is a combination of record lock and gap lock to ensure data consistency.

The main reasons for poor MySQL query performance include not using indexes, wrong execution plan selection by the query optimizer, unreasonable table design, excessive data volume and lock competition. 1. No index causes slow querying, and adding indexes can significantly improve performance. 2. Use the EXPLAIN command to analyze the query plan and find out the optimizer error. 3. Reconstructing the table structure and optimizing JOIN conditions can improve table design problems. 4. When the data volume is large, partitioning and table division strategies are adopted. 5. In a high concurrency environment, optimizing transactions and locking strategies can reduce lock competition.

In database optimization, indexing strategies should be selected according to query requirements: 1. When the query involves multiple columns and the order of conditions is fixed, use composite indexes; 2. When the query involves multiple columns but the order of conditions is not fixed, use multiple single-column indexes. Composite indexes are suitable for optimizing multi-column queries, while single-column indexes are suitable for single-column queries.

To optimize MySQL slow query, slowquerylog and performance_schema need to be used: 1. Enable slowquerylog and set thresholds to record slow query; 2. Use performance_schema to analyze query execution details, find out performance bottlenecks and optimize.

MySQL and SQL are essential skills for developers. 1.MySQL is an open source relational database management system, and SQL is the standard language used to manage and operate databases. 2.MySQL supports multiple storage engines through efficient data storage and retrieval functions, and SQL completes complex data operations through simple statements. 3. Examples of usage include basic queries and advanced queries, such as filtering and sorting by condition. 4. Common errors include syntax errors and performance issues, which can be optimized by checking SQL statements and using EXPLAIN commands. 5. Performance optimization techniques include using indexes, avoiding full table scanning, optimizing JOIN operations and improving code readability.


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