mysql查看当前会话数

解开MySQL的原代码，进入里面的sql目录修改mysqld.cc找到下面一行：
{ "max_connections", (long*) &max_connections,1000,1,16384,0,1},
把它改为：
{ "max_connections", (long*) &max_connections,1000,1,16384,0,1},
存盘退出，然后./configure ;make;make install可以获得同样的效果。

(root@localhost 23:43:30) [mysql]> select version();
+-----------+
| version() |
+-----------+
| 8.0.29    |
+-----------+
1 row in set (0.43 sec)

mysql -h localhost -u username -p

pip install mysql-connector-python

DROP TABLE IF EXISTS `sessions`;
CREATE TABLE `sessions` (
`session_id` varchar(32) NOT NULL default '',
`user_id` int(10) unsigned NOT NULL default '0',
`data_value` text NOT NULL,
`last_visit` timestamp(14) NOT NULL,
PRIMARY KEY (`session_id`),
KEY `user_id` (`user_id`)
) TYPE=MyISAM;

mysql -u <username> -p

SHOW PROCESSLIST;

SELECT SESSION_ID() AS session_id;

SHOW STATUS LIKE 'Threads_connected';

mysql -u 用户名 -p 密码

select id, db, user, host, command, time, state, info
from information_schema.processlist
where command != 'Sleep'
order by time desc

select id, db, user, host, command, time, state, info
from information_schema.processlist
where command != 'Sleep'
order by time desc

general_log = 1
general_log_file = /var/log/mysql/general_sql.log

SHOW VARIABLES LIKE 'autocommit';
SHOW VARIABLES LIKE 'transaction_isolation';
SHOW VARIABLES LIKE 'character_set_client';
SHOW VARIABLES LIKE 'character_set_connection';
SHOW VARIABLES LIKE 'character_set_results';
SHOW VARIABLES LIKE 'sql_mode';

show global variables like 'var_name'; //查看全局系统变量的值，可使用%通配符
show session variables like 'var_name'; //查看会话系统变量的值
show variables like 'var_name'; //优先返回会话系统变量，若会话系统变量不存在，则返回全局系统变量。
# 也可用select查询某个特定参数
select @@global.var_name; //全局系统变量
select @@session.var_name; //会话系统变量
select @@var_name; //优先会话系统变量

http {
    upstream myapp1 {
        server srv1.example.com;
        server srv2.example.com;
        server srv3.example.com;
    }

    server {
        listen 80;

        location / {
            proxy_pass http://myapp1;
        }
    }
}

SHOW PROCESSLIST;

import mysql.connector

import mysql.connector

# 连接到数据库服务器
cnx = mysql.connector.connect(user='username', password='password', host='localhost', database='database_name')