调优Mysql性能 随便

set global log-slow-query =1;
set global long-query-time=2;


可用来查询SQL 会执行多少时间，System lock和Table lock 花多少时间等等，对定位一条语句的I/O消耗和CPU消耗 非常重要。
从启动profile之后的所有查询包括错误的语句都会记录。
关闭会话或者set profiling=0 就关闭了。
# 开启profiling
mysql> set profiling=1;
mysql> select * from user limit 1;
mysql> select count(*) from user group by ***al;
# 查看这些语句的profile
mysql> show profiles;
+--------------+----------------+--------------------------------------------------------------+
| Query_ID | Duration     | Query                                                                      |
+--------------+----------------+--------------------------------------------------------------+
|        1        | 0.00013200   | SELECT DATABASE()                                               |
|        2        | 0.00044100   | select * from user limit 2                                      |
|        3        | 1.95544100   | select nick,count(*) from user group by online|
+--------------+----------------+--------------------------------------------------------------+
查看具体一条（Query_ID=3 这一条）语句的profiles，包括CPU和柱塞I/O的情况
show profile cpu,block io for query 3;
show profile  * for query 2;--查看所有