MySQL is a commonly used relational database management system that is widely used in backend data storage of web applications. In MySQL, the number of connections is a very important performance indicator, which determines how many connection requests the system can handle at the same time. Therefore, it is very necessary for system administrators to master the query method of MySQL connection number.
In MySQL, you can query the connection number configuration information of the current system through the "show variables" command. By default, the maximum number of MySQL connections is 151. If you want to modify this value, you can modify the value of the max_connections parameter in the my.cnf file. An example is as follows:
max_connections=500
If you want to check the number of connections in the current system, you can query it through the following command:
show status like 'Threads_connected';
This command will return the connection value of the current system, which indicates the number of clients that have currently established connections with the MySQL server:
Threads_connected 8
It should be noted that, with the above The results of the command query cannot fully reflect the connection status of the system, because some connections may not be successfully established due to abnormal reasons such as the network. Therefore, if you want to view the connection status more comprehensively, you can use the "show processlist" command.
The "show processlist" command will return detailed information about all connections in the current system, including connection type, user, host, status, execution time, etc. Examples are as follows:
Id | User | Host | db | Command | Time | State | Info
1 | root | localhost | NULL | Query | 0 | init | show processlist
2 | testuser | localhost | testdb | Sleep | 10 | | NULL
3 | testuser | localhost | testdb | Sleep | 5 | | NULL
It can be seen from this result that there are 3 connections in the current system, among which The connection with id 1 is a query request initiated locally by the root user; the connections with id 2 and 3 are Sleep requests initiated by the same testuser user locally to connect to the testdb database, indicating that these two connections are currently No action was performed.
In MySQL, too many connections will cause system resources to be exhausted, thus affecting system performance. Therefore, system administrators should check the number of connections regularly to detect and solve excessive connection problems in a timely manner. At the same time, it is recommended that administrators reasonably adjust the max_connections parameter value to meet the actual usage needs of the system.
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