mysql> show variables like "%long%";    <SPAN style="COLOR: #ff00ff"> //查看一下默认为慢查询的时间10秒 </SPAN> 
+-----------------+-----------+  
| Variable_name  | Value   |  
+-----------------+-----------+  
| long_query_time | 10.000000 |  
+-----------------+-----------+  
1 row in set (0.00 sec)  
  
mysql> set global long_query_time=1;     <SPAN style="COLOR: #ff00ff">//设置成1秒，加上global,下次进mysql已然生效</SPAN>  
Query OK, 0 rows affected (0.00 sec)  
 
mysql> show variables like "%slow%";     <SPAN style="COLOR: #ff00ff"> //查看一下慢查询是不是已经开启 </SPAN> 
+---------------------+---------------------------------+  
| 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';          <SPAN style="COLOR: #ff00ff"> //加上global，不然会报错的</SPAN> 
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';      <SPAN style="COLOR: #ff00ff">//这个参数设置为ON，表示启用慢查询，可以捕获执行时间超过一定数值的SQL语句。</SPAN> 
Query OK, 0 rows affected (0.28 sec)  
  
mysql> show variables like "%slow%";       <SPAN style="COLOR: #ff00ff">//查看是否已经开启 </SPAN> 
+---------------------+---------------------------------+  
| 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)

/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;

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