mysql> show variables like "%long%";         //查看一下默认为慢查询的时间10秒

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

| Variable_name   | Value     |

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

| long_query_time | 10.000000 |

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

1 row in set (0.00 sec)

mysql> set global long_query_time=2;          //设置成2秒，加上global,下次进mysql已然生效

Query OK, 0 rows affected (0.00 sec)

mysql> show variables like "%slow%";          //查看一下慢查询是不是已经开启

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

| Variable_name       | Value                           |

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

| log_slow_queries    | OFF                             |

| slow_launch_time    | 2                               |

| slow_query_log      | OFF                             |

| slow_query_log_file | /usr/local/mysql/mysql-slow.log |

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

4 rows in set (0.00 sec)

mysql> set slow_query_log='ON';                        //加上global，不然会报错的。

ERROR 1229 (HY000): Variable 'slow_query_log' is a GLOBAL variable and should be set with SET GLOBAL

mysql> set global slow_query_log='ON';            //启用慢查询

Query OK, 0 rows affected (0.28 sec)

mysql> show variables like "%slow%";              //查看是否已经开启

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

| Variable_name       | Value                           |

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

| log_slow_queries    | ON                              |

| slow_launch_time    | 2                               |

| slow_query_log      | ON                              |

| slow_query_log_file | /usr/local/mysql/mysql-slow.log |

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

4 rows in set (0.00 sec)

long_query_time = 2

log-slow-queries = /usr/local/mysql/mysql-slow.log  

[root@BlackGhost mysql]# cat mysql-slow.log     //查看命令

/usr/local/mysql/libexec/mysqld, Version: 5.1.26-rc-log (Source distribution). started with:

Tcp port: 3306  Unix socket: /tmp/mysql.sock

Time                 Id Command    Argument

# Time: 100814 13:28:30

# User@Host: root[root] @ localhost []

# Query_time: 10.096500  Lock_time: 0.045791 Rows_sent: 1  Rows_examined: 2374192

SET timestamp=1281763710;

select count(distinct ad_code) as x from ad_visit_history where ad_code in (select ad_code from ad_list where media_id=15);

# Time: 100814 13:37:02

# User@Host: root[root] @ localhost []

# Query_time: 10.394134  Lock_time: 0.000091 Rows_sent: 1  Rows_examined: 2374192

SET timestamp=1281764222;

select count(distinct ad_code) as x from ad_visit_history where ad_code in (select ad_code from ad_list where media_id=15);

# Time: 100814 13:37:16

# User@Host: root[root] @ localhost []

# Query_time: 4.608920  Lock_time: 0.000078 Rows_sent: 1  Rows_examined: 1260544

SET timestamp=1281764236;

select count(*) as cou  from ad_visit_history where ad_code in (select ad_code from ad_list where id=41) order by id desc;

[root@BlackGhost bin]# mysqldumpslow -h

Option h requires an argument

ERROR: bad option

Usage: mysqldumpslow [ OPTS... ] [ LOGS... ]

Parse and summarize the MySQL slow query log. Options are

 --verbose    verbose

 --debug      debug

 --help       write this text to standard output

 -v           verbose

 -d           debug          //查错

 -s ORDER     what to sort by (t, at, l, al, r, ar etc), 'at' is default     //排序方式query次数，时间，lock的时间和返回的记录数来排序
　　　　　　　　// 是表示按照何种方式排序，c、t、l、r分别是按照记录次数、时间、查询时间、返回的记录数来排序，ac、at、al、ar，表示相应的倒叙；

 -r           reverse the sort order (largest last instead of first)       //倒排序

 -t NUM       just show the top n queries                                       //显示前N多个

 -a           don't abstract all numbers to N and strings to 'S'

 -n NUM       abstract numbers with at least n digits within names   //抽象的数字，至 少有n位内的名称

 -g PATTERN   grep: only consider stmts that include this string      //配置模式 后边可以写一个正则匹配模式，大小写不敏感的；

 -h HOSTNAME  hostname of db server for *-slow.log filename (can be wildcard),     //mysql所以机器名或者IP

 default is '*', i.e. match all

 -i NAME      name of server instance (if using mysql.server startup script)

 -l           don't subtract lock time from total time           //总时间中不减去锁定时间

// 例子

[root@BlackGhost bin]# ./mysqldumpslow -s r -t 20 /usr/local/mysql/mysql-slow.log

[root@BlackGhost bin]# ./mysqldumpslow -s r -t 20 -g 'count' /usr/local/mysql/mysql-slow.log