mysqladmin -uroot -paixocm version --gt; 通过mysqladmin查看数据库版本
mysqladmin MySQL客户端管理工具
flush-hosts Flush all cached hosts (max_connect_errors)
刷新主机缓冲中的所有信息
flush-logs Flush all logs
刷新所有日志
flush-status Clear status variables
清除状态变量
flush-tables Flush all tables
刷新所有表
flush-threads Flush the thread cache
刷新线程缓存
flush-privileges Reload grant tables (same as reload)
重新载入授权表(类似reload)
create db_name Create a new database named db_name.
debug Tell the server to write debug information to the error log.
drop db_name Delete the database named db_name and all its tables.
extended-status Display the server status variables and their values.
kill id,id,...
old-password new-password 修改密码
password new-password 设置一个新密码
-------------------------------------------------------------------------
# mysqladmin -uroot password aixocm 给root设置一个密码
# mysqladmin -uroot -p proc stat 查看Mysql的状态值
Enter password:
+----+------+-----------+----+---------+------+-------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+------+-----------+----+---------+------+-------+------------------+
| 8 | root | localhost | | Query | 0 | | show processlist |
+----+------+-----------+----+---------+------+-------+------------------+
Uptime: 148 Threads: 1 Questions: 8
Slow queries: 0 Opens: 33 Flush tables: 1
Open tables: 26 Queries per second avg: 0.054
Uptime --> MySQL服务器已经运行的秒数
Threads --> 活动线程(客户)的数目
Questions --> 服务器启动以来客户的问题(查询)数目
Slow Query --> 执行时间超过long_query_time秒的查询的数量
Opens --> 服务器已经打开的数据库表的数量
Flush tables --> 服务器已经执行的flush ...、refresh和reload命令的数量
Open tables --> 目前打开的表的数量
# mysqladmin -uroot -paixocm version --> 通过mysqladmin查看数据库版本
mysqladmin Ver 8.42 Distrib 5.1.52, for RedHat-linux-gnu on i386
Copyright 2000-2008 MySQL AB, 2008 Sun Microsystems, Inc.
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license
Server version 5.5.20-ndb-7.2.5
Protocol version 10
Connection Localhost via UNIX socket
UNIX socket /var/lib/mysql/mysql.sock
Uptime: 4 min 8 sec
Threads: 1 Questions: 9 Slow queries: 0 Opens: 33 Flush tables: 1 Open tables: 26 Queries per second avg: 0.036

MySQL functions can be used for data processing and calculation. 1. Basic usage includes string processing, date calculation and mathematical operations. 2. Advanced usage involves combining multiple functions to implement complex operations. 3. Performance optimization requires avoiding the use of functions in the WHERE clause and using GROUPBY and temporary tables.

Efficient methods for batch inserting data in MySQL include: 1. Using INSERTINTO...VALUES syntax, 2. Using LOADDATAINFILE command, 3. Using transaction processing, 4. Adjust batch size, 5. Disable indexing, 6. Using INSERTIGNORE or INSERT...ONDUPLICATEKEYUPDATE, these methods can significantly improve database operation efficiency.

In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.

Use the EXPLAIN command to analyze the execution plan of MySQL queries. 1. The EXPLAIN command displays the execution plan of the query to help find performance bottlenecks. 2. The execution plan includes fields such as id, select_type, table, type, possible_keys, key, key_len, ref, rows and Extra. 3. According to the execution plan, you can optimize queries by adding indexes, avoiding full table scans, optimizing JOIN operations, and using overlay indexes.

Subqueries can improve the efficiency of MySQL query. 1) Subquery simplifies complex query logic, such as filtering data and calculating aggregated values. 2) MySQL optimizer may convert subqueries to JOIN operations to improve performance. 3) Using EXISTS instead of IN can avoid multiple rows returning errors. 4) Optimization strategies include avoiding related subqueries, using EXISTS, index optimization, and avoiding subquery nesting.

Methods for configuring character sets and collations in MySQL include: 1. Setting the character sets and collations at the server level: SETNAMES'utf8'; SETCHARACTERSETutf8; SETCOLLATION_CONNECTION='utf8_general_ci'; 2. Create a database that uses specific character sets and collations: CREATEDATABASEexample_dbCHARACTERSETutf8COLLATEutf8_general_ci; 3. Specify character sets and collations when creating a table: CREATETABLEexample_table(idINT

To safely and thoroughly uninstall MySQL and clean all residual files, follow the following steps: 1. Stop MySQL service; 2. Uninstall MySQL packages; 3. Clean configuration files and data directories; 4. Verify that the uninstallation is thorough.

Renaming a database in MySQL requires indirect methods. The steps are as follows: 1. Create a new database; 2. Use mysqldump to export the old database; 3. Import the data into the new database; 4. Delete the old database.


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