在mysql查询性能分析中最常用的就是explain了，profile查看一些具体的性能也是不错的 1. profile 我们可以先使用 SELECT @@profiling; 来查看是否已经启用profile，如果profilng值为0，可以通过 SET profiling = 1; 来启用。启用profiling之后，我们执行一条查询语句，比如： select count(*) from roi_summary; 然后show profiles查看如下： +----------+------------+----------------------------------+ | Query_ID | Duration | Query | +----------+------------+----------------------------------+ | 1 | 0.00021500 | select @@profiling | | 2 | 0.05522700 | select count(*) from roi_summary | +----------+------------+----------------------------------+ 2 rows in set (0.00 sec) 其中ID为5的语句是刚执行的查询语句，这时候我们执行show profile for query 2来查看这条语句的执行过程如下; +--------------------------------+----------+ | Status | Duration | +--------------------------------+----------+ | starting | 0.000021 | | checking query cache for query | 0.000045 | | checking permissions | 0.000007 | | Opening tables | 0.000011 | | System lock | 0.000004 | | Table lock | 0.000040 | | init | 0.000012 | | optimizing | 0.000005 | | statistics | 0.000010 | | preparing | 0.000010 | | executing | 0.000005 | | Sending data | 0.055021 | | end | 0.000007 | | end | 0.000004 | | query end | 0.000003 | | storing result in query cache | 0.000004 | | freeing items | 0.000008 | | closing tables | 0.000005 | | logging slow query | 0.000002 | | cleaning up | 0.000003 | +--------------------------------+----------+ 20 rows in set (0.00 sec) 可以看出此条查询语句的执行过程及执行时间，总的时间约为0.05s。 这时候我们再执行一次 select count(*) from roi_summary; show profiles; +----------+------------+----------------------------------+ | Query_ID | Duration | Query | +----------+------------+----------------------------------+ | 1 | 0.00021500 | select @@profiling | | 2 | 0.05522700 | select count(*) from roi_summary | | 3 | 0.00006000 | select count(*) from roi_summary | +----------+------------+----------------------------------+ 然后执行show profile for query 3来查看本条语句的执行过程 +--------------------------------+----------+ | Status | Duration | +--------------------------------+----------+ | starting | 0.000016 | | checking query cache for query | 0.000007 | | checking privileges on cached | 0.000004 | | checking permissions | 0.000005 | | sending cached result to clien | 0.000022 | | logging slow query | 0.000003 | | cleaning up | 0.000003 | +--------------------------------+----------+ 可以看出此次第二次查询因为前一次的查询生成了cache，所以这次无需从数据库文件中再次读取数据而是直接从缓存中读取，结果查询时间比第一次快了N倍。 2. explain 至于EXPLAIN 官方文档讲解的相当详细了，
查看更多关于mysql的explain与profile概述的详细内容...