MySQL性能优化10大核心技巧

MySQL查询性能优化核心知识点总结

索引优化策略

合理使用索引是提升查询性能的基础。B-Tree索引适合等值查询和范围查询，哈希索引仅适用于等值查询。复合索引需遵循最左前缀原则，避免冗余索引。

定期分析慢查询日志定位低效SQL，使用EXPLAIN查看执行计划，关注type字段（应避免ALL或index）和Extra字段（避免Using filesort或Using temporary）。

查询语句优化

避免SELECT *，只查询必要字段。使用连接（JOIN）替代子查询时，确保关联字段有索引。大表分页使用延迟关联：

SELECT t1.* FROM large_table t1 
JOIN (SELECT id FROM large_table LIMIT 1000000, 10) t2 ON t1.id = t2.id;

对于IN和EXISTS，数据量小时IN更高效，大表关联时EXISTS可能更优。

数据库设计优化

表设计遵循第三范式，但高频查询场景可适当冗余。字段类型选择精确，如用INT而非VARCHAR存储数字。大字段（如TEXT）拆分到单独表避免影响主表性能。

分库分表策略：水平分表按哈希或范围拆分，垂直分表按字段热度分离。

配置与硬件优化

调整innodb_buffer_pool_size为物理内存的70%-80%。优化query_cache_size（适用于读多写少场景）。SSD硬盘显著提升I/O性能，RAID10保障数据安全与读写速度。

高级技巧

使用覆盖索引（索引包含查询所需全部字段）避免回表。对于统计类查询，考虑预计算或物化视图。批量操作替代循环单条操作，减少网络与事务开销。

定期执行ANALYZE TABLE更新统计信息，避免优化器误判。

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