Mysql使用profile分析sql开销的代码

1.使用之前先查看当前数据库的版本信息,低版本无法使用.
 show version(); 或者 show variables like '%version%'
2.查看profiling
 show variables like '%profil%' ;

 result:
 +------------------------+-------+ 
 | Variable_name | Value | 
 +------------------------+-------+ 
 | have_profiling | YES | --只读变量，用于控制是否由系统变量开启或禁用profiling 
 | profiling | OFF | --开启SQL语句剖析功能 
 | profiling_history_size | 15 | --设置保留profiling的数目，缺省为15，范围为0至100，为0时将禁用p

 show profiles; 查看是否开启,效果同上.
3.查看使用说明 
 help profile;
4.开启profile
 set profiling=1; 赋值时候不要有多余的空格.
5.运行sql,查看对应的profile
 select * from test ;
 show profiles; 

 result:
 +----------+------------+--------------------------------------------------------------------------------------------------------------------------+
 | Query_ID | Duration | Query |
 +----------+------------+--------------------------------------------------------------------------------------------------------------------------+
 | 28 | 0.00033575 | select * from test |
 +----------+------------+--------------------------------------------------------------------------------------------------------------------------+

 分析sql性能,分析的时候可以加上对应的开销字段
 show profile [cpu,io][all] for query 28 ;

 show profile for query 28 ;

 +----------------------+----------+
 | Status | Duration |
 +----------------------+----------+
 | starting | 5.7E-5 |
 | checking permissions | 7E-6 |
 | Opening tables | 1.7E-5 |
 | init | 2.3E-5 |
 | System lock | 8E-6 |
 | optimizing | 5E-6 |
 | statistics | 1.1E-5 |
 | preparing | 9E-6 |
 | executing | 3E-6 |
 | Sending data | 8.8E-5 |
 | end | 5E-6 |
 | query end | 6E-6 |
 | closing tables | 5E-6 |
 | freeing items | 7.8E-5 |
 | cleaning up | 1.5E-5 |
 +----------------------+----------+
6.关闭
 set profiling=off;