Explanation of MySQL Server variables (1)

Autocommit {0 | 1} sets whether MySQL transactions are automatically committed. 1 indicates immediate commit, and 0 indicates explicit commit. The role is global or session and can be used in the configuration file (but not in versions earlier than 5.5.8)

Autocommit = {0 | 1} sets whether MySQL transactions are automatically committed. 1 indicates immediate submission, and 0 indicates explicit submission. The role is global or session and can be used in the configuration file (but not in versions earlier than 5.5.8)

Autocommit = {0 | 1}

Sets whether MySQL transactions are automatically committed. 1 indicates immediate submission, and 0 indicates explicit submission. Global or session is a dynamic variable that can be used in the configuration file (but not in versions earlier than 5.5.8.

Automatic_sp_privileges = {0 | 1}

Set whether the MySQL server grants the EXECUTE and alter routine permissions on the created storage ROUTINE to the creation of the storage ROUTINE. The default value is 1 (grant the two permissions to the Creator ). The scope is global.

Back_log = #

When a MySQL main thread receives a large number of connection requests within a short period of time, it will take some time to detect a thread and start a new thread for the new request, the value of the back_log parameter is the number of accepted requests that arrive within a short period of time and waits for the main MySQL thread for subsequent processing. The function scope is global. You can use a configuration file that is not a dynamic variable.

Basedir = PATH,-B PATH

It is used to specify the installation directory of MySQL. All other common relative paths are relative to the path here. It has a global scope and can be used in the configuration file but is not a dynamic variable.

Bind-address = ADDR

Specify the IP address of the mysqld service listener. The default value is 0.0.0.0, indicating all IP addresses configured on the local machine. It has a global scope and can be used in the configuration file but is not a dynamic variable.

Binlog-format = {ROW | STATEMENT | MIXED}

Specifies the binary log type. The default value is STATEMENT. If the binary log format is set but the binary log is not enabled, the warning log is generated and recorded in the error log at MySQL startup. Global or session is used in configuration files and is a dynamic variable.

Buld_insert_buffer_size

The MyISAM engine uses a special tree-structured cache to accelerate batch INSERT operations, such as INSERT... SELECT, INSERT... VALUES (...), (...),... and load data infile commands. For each thread, the buffer size is independent, and the configured value unit is byte. The valid value range is 0 to the power of "2 ^ CPU length, the default size is 8 MB. Global or session is used as the configuration file and is a dynamic variable.

Chroot = PATH,-r PATH

Set the working directory of MySQL when working in the chroot mode. This is a recommended mechanism in environments where security issues are particularly important. However, the operation of commands such as load data infile may be affected. Can be used in configuration files.

Console

This function is only applicable to the Windows platform and is used to send error log information to standard input and error output. This function is equally effective even if the -- log-error option is configured.

Concurrent_insert = {NEVER | AUTO | ALWAYS} or use {0 | 1 | 2}

Set whether to allow parallel INSERT and SELECT statements on MyISAM tables. It has a global scope and can be used in configuration files and is a dynamic variable.

Connect_timeout = #

The number of seconds that the mysqld server waits before responding to the "failed handshake operation" message to the client. The default value is 10 seconds. It has a global scope and can be used in configuration files and is a dynamic variable.

Core-file

When the MySQL process goes down, the information is saved as a core file. On the Linux platform, the core file is usually saved to the working directory of the current process and named as core. pid, whose file name suffix pid is the process Number of the current process; For MySQL, the SAVE directory is the data file directory.

Datadir = PATH,-h PATH

Specifies the data directory of the MySQL service. The function is global and can be used for the Hong Kong server in the configuration file, but is not a dynamic variable.

Default_storage_engine = {Engine_Name}

Set the default storage engine for the MySQL server. Before MySQL 5.5.5, the default value is MyISAM, and later versions are InnoDB by default. It has a global scope and can be used in configuration files and is a dynamic variable.

Delay-key-write = {ON | OFF | ALL}

Only used for MyISAM tables, and the DELAY_KEY_WRITE option must be used when creating a table. When enabled, the key buffer is not cleared during each index update, but is cleared only when the table is closed. OFF indicates that DELAY_KEY_WRITE is ignored, and ON indicates that MySQL accepts any DELAY_KEY_WRITE option used when creating TABLE. ALL indicates that ALL newly opened tables follow this feature.

Error-count

Number of error messages caused by the previous SQL statement. This is a read-only variable.

Event-schedabled = {ON | OFF | DISABLED}

Set whether the MySQL server is enabled and whether to enable Event Scheduler. OFF indicates stop, which is the default value; ON indicates start, which is running and executes all scheduling transactions; DISABLED indicates that Event Scheduler is DISABLED, that is, it cannot be switched to start. It has a global scope and can be used in configuration files and is a dynamic variable.

Expire_logs_days = {0 .. 99}

Sets the Expiration days of binary logs. binary log files that exceed the specified days are automatically deleted. The default value is 0, indicating that the expired automatic deletion function is not enabled. If this function is enabled, automatic deletion usually occurs at MySQL startup or FLUSH logs. It has a global scope and can be used in configuration files and is a dynamic variable.

External_user = name

When using the authentication plug-in on the MySQL server for user authentication, this plug-in will initiate a connection request to the user as another user for permission check purposes, in this way, external users can act as the proxy users of the second user and have all the permissions of the second user. When MySQL's internal authentication mechanism is used or no plug-in sets a value for it, the value of this variable is NULL. The function scope is session level. It cannot be used in configuration files and is a non-dynamic variable.

Flush = {ON | OFF}

Sets whether the MySQL server executes data synchronization for each SQL statement separately (writes data to the disk ). Under normal circumstances, MySQL executes data synchronization for each statement and submits the subsequent synchronization process to the operating system. The default value is OFF. It has a global scope and can be used in configuration files and is a dynamic variable.

Flush-time = {0 ..}

If the value is not 0, the MySQL server will close all opened tables at a time specified by flush_time and use them to release all resources and synchronize data to the disk. This feature must be enabled only when system resources are extremely scarce. The default value is 0. It has a global scope and can be used in configuration files and is a dynamic variable.

Foreign-key-checks = {0 | 1}

Set whether it is an InnoDB table check foreign key constraint. The default value is 1, that is, check. Disable this function to avoid the side effects of foreign key constraints when you do not ensure that all InnoDB tables are reloaded in the original order.

General_log = {ON | OFF}

Set whether to enable query logs. The default value is determined by whether the -- general_log option is used when mysqld is started. If this option is enabled, the output location is defined by the -- log_output option. If the value of log_output is set to NONE, the query log is enabled, and no log information is recorded. It has a global scope and can be used in configuration files and is a dynamic variable.

General_log_file = FILE_NAME

The name of the log file to query. The default value is "hostname. log ". It has a global scope and can be used in configuration files and is a dynamic variable.

Group_concat_max_len = {4 ..}

Sets the maximum length of the value returned by the GROUP_CONCAT () function. The default value is 1024. Valid value range: 4 to the power of "2 ^ CPU length. It is a global or session-level configuration file that is a dynamic variable.

Have-compress = {YES | NO}

Whether the zlib compression library can be used by the MySQL server. When the value is NO, the COMPRESS () and UNCOMPRESS () functions are unavailable.

Have_crypt = {YES | NO}

Whether the crypt () system call can be used by the MySQL server. When the value is NO, the ENCRYPT () function is unavailable.

Have_csv = {YES | NO}

If mysqld supports the CSV engine, YES is used; otherwise, NO is used.

Have_dynamic_loading = {YES | NO}

Mysqld supports YES when dynamically loading plug-ins; otherwise, NO.

Have_geometry = {YES | NO}

If mysqld supports the spatial data type, the value is YES; otherwise, the value is NO.

Have_innodb = {YES | NO}

If mysqld supports the InnoDB Storage engine, YES is used; otherwise, NO is used.

Have_openssl = {YES | NO}

This is the alias of the have_ssl option;

Have_ssl = {YES | NO}

If mysqld supports SSL connections, YES is used; otherwise, NO is used. DISABLED indicates that SSL support is enabled during mysqld compilation, but the correct ssl-xxx class (such as ssl_cert) option is not available when mysqld is started.

Have_partitioning = {YES | NO}

Whether mysqld supports partitioning. This option is obsolete and removed from the MySQL-5.6, which can be obtained using show engines.

Have_profiling = {YES | NO}

When mysqld supports statement performance analysis, the value is YES; otherwise, the value is NO. If the profiling function is supported, the -- profiling variable is used to control whether to enable this function.

Have_query_cache = {YES | NO}

If mysqld supports query cache, the value is YES; otherwise, the value is NO.

Have_rtree_keys = {YES | NO}

If mysqld supports the RTREE index, the value is YES; otherwise, the value is NO. The RTREE index is used for the spatial index of the MyISAM table.

Have_symlink = {YES | NO}

If mysqld supports symbolic links, the value is YES; otherwise, the value is NO. On Unix hosts, this function is useful for Data Directories and index directories.

Hostname = STRING

When the mysqld server is started, the host name is assigned to this variable. It is a non-dynamic variable with a global scope.

Identity

The synonym of the last_insert_id variable, website space, mainly exists to be compatible with other database systems. Session-level variables.

Init_connect = STRING