1)我们先通过status命令查看Mysql运行状态，如下：

mysql> status;

--------------

mysql  Ver 14.12 Distrib 5.0.77, for redhat-linux-gnu (x86_64) using readline 5.1

Connection id:          19878

Current database:

Current user:           root@localhost

SSL:                    Not in use

Current pager:          stdout

Using outfile:          ''

Using delimiter:        ;

Server version:         5.0.77 Source distribution

Protocol version:       10

Connection:             Localhost via UNIX socket

Server characterset:    latin1

Db     characterset:    latin1

Client characterset:    latin1

Conn.  characterset:    latin1

UNIX socket:            /var/lib/mysql/mysql.sock

Uptime:                 312 days 31 min 37 sec

Threads: 1  Questions: 107979  Slow queries: 0  Opens: 17  Flush tables: 1  Open tables: 11 Queries per second avg: 0.004

--------------

在上面显示列表的最后一条，我们来查看Slow queries这一项的值，如果多次查看的值大于0的话,说明有些查询sql命令执行时间过长。

2)这时再通过show processlist命令来查看当前正在运行的SQL，从中找出运行慢的SQL语句，找到执行慢的语句后，再用explain命令查看这些语句的执行计划。

mysql> show processlist;

+-------+------+-----------+------+---------+------+-------+------------------+

| Id    | User | Host      | db   | Command | Time | State | Info             |

+-------+------+-----------+------+---------+------+-------+------------------+

| 19878 | root | localhost | NULL | Query   |    0 | NULL  | show processlist |

+-------+------+-----------+------+---------+------+-------+------------------+

1 row in set (0.00 sec)

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2012-02-15 21:35

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