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) 
 

在[mysqld]里面加上以下内容
long_query_time = 2 
log-slow-queries = /usr/local/mysql/mysql-slow.log 
重启mysql
/usr/local/mysql/libexec/mysqld restart

[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 
# : 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 
# : 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 
# : 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 
 -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
 -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  
 

[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