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slow query log查询慢查询语句 Slow query log 慢查询日志，通过设置相关的慢查询参数，可以把数据库慢的sql语句输出到日志，这就是慢查询日志，很多情况下，考虑到性能问题，慢查询日志是不打开的，即不进行慢查询日志的输出，也许有时候为了查找慢查询语句，会临时打开，这是找寻低效率sql的一种方式,下面看一下参数 mysql>show variables like '%slow%'; +------------------+-------+ | Variable_name | Value | +------------------+-------+ | log_slow_queries | OFF | | slow_launch_time | 2 | +------------------+-------+ 2 rows in set (0.00 sec) log_slow_queries 默认是关闭的，设置为 on则打开，有慢查询日志输出。Slow_launch_time设置慢查询标准，定义时间值，最小设置为1秒，查询时间超过这个值的将会输出到日志中。想找出1秒以下的慢查询标准，可以使用percona提供的microslow-patch来突破限制，将慢查询时间减小到毫秒级别。 作者 aeolus_pu bitsCN.com
What are stored procedures in MySQL?May 01, 2025 am 12:27 AMStored procedures are precompiled SQL statements in MySQL for improving performance and simplifying complex operations. 1. Improve performance: After the first compilation, subsequent calls do not need to be recompiled. 2. Improve security: Restrict data table access through permission control. 3. Simplify complex operations: combine multiple SQL statements to simplify application layer logic.
How does query caching work in MySQL?May 01, 2025 am 12:26 AMThe working principle of MySQL query cache is to store the results of SELECT query, and when the same query is executed again, the cached results are directly returned. 1) Query cache improves database reading performance and finds cached results through hash values. 2) Simple configuration, set query_cache_type and query_cache_size in MySQL configuration file. 3) Use the SQL_NO_CACHE keyword to disable the cache of specific queries. 4) In high-frequency update environments, query cache may cause performance bottlenecks and needs to be optimized for use through monitoring and adjustment of parameters.
What are the advantages of using MySQL over other relational databases?May 01, 2025 am 12:18 AMThe reasons why MySQL is widely used in various projects include: 1. High performance and scalability, supporting multiple storage engines; 2. Easy to use and maintain, simple configuration and rich tools; 3. Rich ecosystem, attracting a large number of community and third-party tool support; 4. Cross-platform support, suitable for multiple operating systems.
How do you handle database upgrades in MySQL?Apr 30, 2025 am 12:28 AMThe steps for upgrading MySQL database include: 1. Backup the database, 2. Stop the current MySQL service, 3. Install the new version of MySQL, 4. Start the new version of MySQL service, 5. Recover the database. Compatibility issues are required during the upgrade process, and advanced tools such as PerconaToolkit can be used for testing and optimization.
What are the different backup strategies you can use for MySQL?Apr 30, 2025 am 12:28 AMMySQL backup policies include logical backup, physical backup, incremental backup, replication-based backup, and cloud backup. 1. Logical backup uses mysqldump to export database structure and data, which is suitable for small databases and version migrations. 2. Physical backups are fast and comprehensive by copying data files, but require database consistency. 3. Incremental backup uses binary logging to record changes, which is suitable for large databases. 4. Replication-based backup reduces the impact on the production system by backing up from the server. 5. Cloud backups such as AmazonRDS provide automation solutions, but costs and control need to be considered. When selecting a policy, database size, downtime tolerance, recovery time, and recovery point goals should be considered.
What is MySQL clustering?Apr 30, 2025 am 12:28 AMMySQLclusteringenhancesdatabaserobustnessandscalabilitybydistributingdataacrossmultiplenodes.ItusestheNDBenginefordatareplicationandfaulttolerance,ensuringhighavailability.Setupinvolvesconfiguringmanagement,data,andSQLnodes,withcarefulmonitoringandpe
How do you optimize database schema design for performance in MySQL?Apr 30, 2025 am 12:27 AMOptimizing database schema design in MySQL can improve performance through the following steps: 1. Index optimization: Create indexes on common query columns, balancing the overhead of query and inserting updates. 2. Table structure optimization: Reduce data redundancy through normalization or anti-normalization and improve access efficiency. 3. Data type selection: Use appropriate data types, such as INT instead of VARCHAR, to reduce storage space. 4. Partitioning and sub-table: For large data volumes, use partitioning and sub-table to disperse data to improve query and maintenance efficiency.
How can you optimize MySQL performance?Apr 30, 2025 am 12:26 AMTooptimizeMySQLperformance,followthesesteps:1)Implementproperindexingtospeedupqueries,2)UseEXPLAINtoanalyzeandoptimizequeryperformance,3)Adjustserverconfigurationsettingslikeinnodb_buffer_pool_sizeandmax_connections,4)Usepartitioningforlargetablestoi
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