MySQL，查看连接数和状态等

1、MySQL> show status like '%connect%';

   Connections，试图连接到（不管是否成功）MySQL服务器的连接数。
   Max_used_connections，服务器启动后已经同时使用的连接的最大数量。
   Threads_connected，当前的连接数。

2、mysql> show variables like '%connect%';

   max_connections，最大连接数。

3、修改max_connections

   在配置文件（my.cnf或my.ini）在最下面，天加一句：
   max_connections=32000
   然后，用命令重启：/etc/init.d/mysqld restart
   虽然这里写的32000，实际MySQL服务器允许的最大连接数16384；
   添加了最大允许连接数，对系统消耗增加不大。

4、mysql> show processlist;
显示当前正在执行的MySQL连接。

mysql> show status like '%connect%';  
+-----------------------------------------------+-------+
| Variable_name                                 | Value |
+-----------------------------------------------+-------+
| Aborted_connects                              | 2     |
| Connection_errors_accept                      | 0     |
| Connection_errors_internal                    | 0     |
| Connection_errors_max_connections             | 0     |
| Connection_errors_peer_address                | 0     |
| Connection_errors_select                      | 0     |
| Connection_errors_tcpwrap                     | 0     |
| Connections                                   | 445   |
| Max_used_connections                          | 61    |
| Performance_schema_session_connect_attrs_lost | 0     |
| Ssl_client_connects                           | 0     |
| Ssl_connect_renegotiates                      | 0     |
| Ssl_finished_connects                         | 0     |
| Threads_connected                             | 57    |
+-----------------------------------------------+-------+
14 rows in set (0.00 sec)

mysql> show variables like '%connect%'; 
+-----------------------------------------------+-----------------+
| Variable_name                                 | Value           |
+-----------------------------------------------+-----------------+
| character_set_connection                      | utf8            |
| collation_connection                          | utf8_general_ci |
| connect_timeout                               | 10              |
| disconnect_on_expired_password                | ON              |
| init_connect                                  |                 |
| max_connect_errors                            | 100             |
| max_connections                               | 151             |
| max_user_connections                          | 0               |
| performance_schema_session_connect_attrs_size | 512             |
+-----------------------------------------------+-----------------+
9 rows in set (0.00 sec)

mysql> show processlist;  
+-----+------+---------------------+------+---------+------+-------+------------------+
| Id  | User | Host                | db   | Command | Time | State | Info             |
+-----+------+---------------------+------+---------+------+-------+------------------+
| 315 | srea | 192.168.0.206:58566 | srea | Sleep   | 3370 |       | NULL             |
| 316 | srea | 192.168.0.206:58567 | srea | Sleep   | 3370 |       | NULL             |
| 317 | srea | 192.168.0.206:58568 | srea | Sleep   | 3370 |       | NULL             |
| 318 | srea | 192.168.0.206:58569 | srea | Sleep   | 3370 |       | NULL             |
| 319 | srea | 192.168.0.206:58570 | srea | Sleep   | 3370 |       | NULL             |
| 320 | srea | 192.168.0.206:58572 | srea | Sleep   | 3370 |       | NULL             |
| 321 | srea | 192.168.0.206:58575 | srea | Sleep   | 3370 |       | NULL             |
| 322 | srea | 192.168.0.206:58576 | srea | Sleep   | 3370 |       | NULL             |
| 323 | srea | 192.168.0.206:58577 | srea | Sleep   | 3370 |       | NULL             |
| 324 | srea | 192.168.0.206:58578 | srea | Sleep   | 3370 |       | NULL             |
| 325 | srea | 192.168.0.206:58579 | srea | Sleep   | 3370 |       | NULL             |
| 326 | srea | 192.168.0.206:58581 | srea | Sleep   | 3370 |       | NULL             |
| 327 | srea | 192.168.0.206:58582 | srea | Sleep   | 3370 |       | NULL             |
| 328 | srea | 192.168.0.206:58583 | srea | Sleep   | 3370 |       | NULL             |
| 329 | srea | 192.168.0.206:58586 | srea | Sleep   | 3370 |       | NULL             |
| 330 | srea | 192.168.0.206:58587 | srea | Sleep   | 3370 |       | NULL             |
| 331 | srea | 192.168.0.206:58589 | srea | Sleep   | 3370 |       | NULL             |
| 332 | srea | 192.168.0.206:58590 | srea | Sleep   | 3370 |       | NULL             |
| 334 | srea | 192.168.0.206:59012 | srea | Sleep   | 2920 |       | NULL             |
| 335 | srea | 192.168.0.206:59342 | srea | Sleep   | 2487 |       | NULL             |
| 336 | srea | 192.168.0.206:59343 | srea | Sleep   | 2545 |       | NULL             |
| 337 | srea | 192.168.0.206:59344 | srea | Sleep   | 2545 |       | NULL             |
| 338 | srea | 192.168.0.206:59345 | srea | Sleep   | 2545 |       | NULL             |
| 339 | srea | 192.168.0.206:59346 | srea | Sleep   | 2545 |       | NULL             |
| 340 | srea | 192.168.0.206:59347 | srea | Sleep   | 2545 |       | NULL             |
| 341 | srea | 192.168.0.206:59348 | srea | Sleep   | 2545 |       | NULL             |
| 342 | srea | 192.168.0.206:59349 | srea | Sleep   | 2544 |       | NULL             |
| 343 | srea | 192.168.0.206:59350 | srea | Sleep   | 2544 |       | NULL             |
| 344 | srea | 192.168.0.206:59351 | srea | Sleep   | 2544 |       | NULL             |
| 345 | srea | 192.168.0.206:59352 | srea | Sleep   | 2544 |       | NULL             |
| 346 | srea | 192.168.0.206:59353 | srea | Sleep   | 2544 |       | NULL             |
| 347 | srea | 192.168.0.206:59354 | srea | Sleep   | 2544 |       | NULL             |
| 348 | srea | 192.168.0.206:59355 | srea | Sleep   | 2544 |       | NULL             |
| 349 | srea | 192.168.0.206:59356 | srea | Sleep   | 2544 |       | NULL             |
| 350 | srea | 192.168.0.206:59357 | srea | Sleep   | 2544 |       | NULL             |
| 351 | srea | 192.168.0.206:59358 | srea | Sleep   | 2544 |       | NULL             |
| 353 | srea | 192.168.0.206:59341 | srea | Sleep   | 2503 |       | NULL             |
| 354 | srea | 192.168.0.206:59340 | srea | Sleep   | 2486 |       | NULL             |
| 418 | srea | 192.168.0.206:52115 | srea | Sleep   |  643 |       | NULL             |
| 419 | srea | 192.168.0.206:52140 | srea | Sleep   |  717 |       | NULL             |
| 420 | srea | 192.168.0.206:52145 | srea | Sleep   |  717 |       | NULL             |
| 421 | srea | 192.168.0.206:52148 | srea | Sleep   |  717 |       | NULL             |
| 422 | srea | 192.168.0.206:52151 | srea | Sleep   |  717 |       | NULL             |
| 423 | srea | 192.168.0.206:52154 | srea | Sleep   |  717 |       | NULL             |
| 424 | srea | 192.168.0.206:52157 | srea | Sleep   |  717 |       | NULL             |
| 425 | srea | 192.168.0.206:52159 | srea | Sleep   |  716 |       | NULL             |
| 426 | srea | 192.168.0.206:52160 | srea | Sleep   |  716 |       | NULL             |
| 427 | srea | 192.168.0.206:52161 | srea | Sleep   |  716 |       | NULL             |
| 428 | srea | 192.168.0.206:52164 | srea | Sleep   |  716 |       | NULL             |
| 429 | srea | 192.168.0.206:52167 | srea | Sleep   |  716 |       | NULL             |
| 430 | srea | 192.168.0.206:52169 | srea | Sleep   |  716 |       | NULL             |
| 431 | srea | 192.168.0.206:52172 | srea | Sleep   |  716 |       | NULL             |
| 432 | srea | 192.168.0.206:52175 | srea | Sleep   |  716 |       | NULL             |
| 433 | srea | 192.168.0.206:52179 | srea | Sleep   |  716 |       | NULL             |
| 436 | srea | 192.168.0.206:52114 | srea | Sleep   |  668 |       | NULL             |
| 437 | srea | 192.168.0.206:52112 | srea | Sleep   |  641 |       | NULL             |
| 444 | root | localhost           | NULL | Query   |    0 | init  | show processlist |
+-----+------+---------------------+------+---------+------+-------+------------------+
57 rows in set (0.00 sec)