在Mysql中，能够经过以下方式查询Mysql数据库当前链接的用户及会话信息：
1. show full processlist
mysql
mysql> show full processlist;
+----------+-----------+--------------------+-------------+---------+------+-------+-----------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----------+-----------+--------------------+-------------+---------+------+-------+-----------------------+
| 26321235 | root | localhost | socialciv | Sleep | 3 | | NULL |
| 26322405 | root | localhost | NULL | Query | 0 | NULL | show full processlist |
| 26322588 | dmadbuser | 192.168.0.51:51395 | user_silo_0 | Sleep | 0 | | NULL |
| 26322621 | dmadbuser | 192.168.0.51:51400 | soooalciv | Sleep | 0 | | NULL |
| 26322645 | dmadbuser | 192.168.0.51:51433 | user_silo_2 | Sleep | 0 | | NULL |
| 26322646 | dmadbuser | 192.168.0.52:42308 | user_silo_1 | Sleep | 1 | | NULL |
| 26322648 | dmadbuser | 192.168.0.51:51439 | user_silo_0 | Sleep | 0 | | NULL |
| 26322650 | dmadbuser | 192.168.0.51:51442 | user_silo_1 | Sleep | 0 | | NULL |
| 26322659 | dmadbuser | 192.168.0.51:51454 | user_silo_1 | Sleep | 1 | | NULL |
| 26322667 | dmadbuser | 192.168.0.51:51469 | soooalciv | Sleep | 0 | | NULL |
| 26322671 | dmadbuser | 192.168.0.51:51475 | user_silo_0 | Sleep | 0 | | NULL |
| 26322674 | dmadbuser | 192.168.0.51:51481 | user_silo_1 | Sleep | 0 | | NULL |
| 26322677 | dmadbuser | 192.168.0.51:51485 | user_silo_1 | Sleep | 0 | | NULL |
| 26322678 | dmadbuser | 192.168.0.52:42356 | user_silo_2 | Sleep | 0 | | NULL |
| 26322679 | dmadbuser | 192.168.0.51:51486 | user_silo_0 | Sleep | 0 | | NULL |
| 26322680 | dmadbuser | 192.168.0.51:51487 | user_silo_1 | Sleep | 0 | | NULL |
| 26322681 | dmadbuser | 192.168.0.52:42359 | user_silo_2 | Sleep | 0 | | NULL |
| 26322684 | dmadbuser | 192.168.0.51:51493 | user_silo_2 | Sleep | 0 | | NULL |
| 26322685 | dmadbuser | 192.168.0.52:42367 | user_silo_1 | Sleep | 0 | | NULL |
| 26322688 | dmadbuser | 192.168.0.51:51500 | user_silo_2 | Sleep | 0 | | NULL |
| 26322689 | dmadbuser | 192.168.0.52:42368 | user_silo_0 | Sleep | 0 | | NULL |
| 26322690 | dmadbuser | 192.168.0.52:42371 | user_silo_1 | Sleep | 0 | | NULL |
+----------+-----------+--------------------+-------------+---------+------+-------+-----------------------+
2. mysqladmin -uroot -p -hlocalhost processlistsql
-bash-3.2$ mysqladmin -uroot -p -hlocalhost processlist
Enter password:
+----------+-----------+--------------------+-------------+---------+------+-------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----------+-----------+--------------------+-------------+---------+------+-------+------------------+
| 26309321 | dmadbuser | 192.168.0.53:33532 | soooalciv | Sleep | 2 | | |
| 26309374 | dmadbuser | 192.168.0.53:33611 | soooalciv | Sleep | 2 | | |
| 26309387 | dmadbuser | 192.168.0.53:33631 | user_silo_1 | Sleep | 3 | | |
| 26309390 | dmadbuser | 192.168.0.53:33636 | user_silo_1 | Sleep | 0 | | |
| 26309393 | dmadbuser | 192.168.0.53:33639 | user_silo_0 | Sleep | 0 | | |
| 26309419 | dmadbuser | 192.168.0.53:33677 | user_silo_2 | Sleep | 2 | | |
| 26309420 | dmadbuser | 192.168.0.53:33679 | user_silo_2 | Sleep | 0 | | |
| 26309424 | dmadbuser | 192.168.0.53:33685 | user_silo_1 | Sleep | 2 | | |
| 26309442 | dmadbuser | 192.168.0.51:33589 | user_silo_1 | Sleep | 1 | | |
| 26309445 | dmadbuser | 192.168.0.53:33723 | user_silo_0 | Sleep | 1 | | |
| 26309457 | dmadbuser | 192.168.0.51:33612 | user_silo_2 | Sleep | 1 | | |
| 26309459 | dmadbuser | 192.168.0.53:33745 | user_silo_1 | Sleep | 1 | | |
| 26309469 | dmadbuser | 192.168.0.53:33759 | user_silo_2 | Sleep | 0 | | |
| 26309470 | dmadbuser | 192.168.0.53:33760 | user_silo_2 | Sleep | 0 | | |
| 26309471 | dmadbuser | 192.168.0.51:33632 | user_silo_2 | Sleep | 0 | | |
| 26309472 | dmadbuser | 192.168.0.53:33763 | user_silo_2 | Sleep | 0 | | |
| 26309473 | root | localhost | | Query | 0 | | show processlist |
+----------+-----------+--------------------+-------------+---------+------+-------+------------------+
max_connections 参数能够用于控制数据库的最大链接数：数据库
mysql> show variables like '%connect%';
+--------------------------+-------------------+
| Variable_name | Value |
+--------------------------+-------------------+
| character_set_connection | latin1 |
| collation_connection | latin1_swedish_ci |
| connect_timeout | 10 |
| init_connect | |
| max_connect_errors | 10 |
| max_connections | 4000 |
| max_user_connections | 0 |
+--------------------------+-------------------+
如下命令用于查询Mysql数据库的状态信息：bash
mysqladmin -uroot -p -hlocalhost status
-bash-3.2$ mysqladmin -uroot -p -hlocalhost status
Enter password:
Uptime: 540120 Threads: 21 Questions: 306833244 Slow queries: 37 Opens: 320214 Flush tables: 19 Open tables: 64 Queries per second avg: 568.083