MySQL statement to query the current number of connections

1. Check the current total number of connections

SHOW STATUS LIKE 'Threads_connected';

Returns the total number of currently established connections

2. Check the maximum number of connections configuration

SHOW VARIABLES LIKE 'max_connections';

Displays the maximum number of concurrent connections allowed by the server

3. View detailed connection information

SHOW PROCESSLIST;

Shows details of all connections (user, source IP, executed SQL, etc.)

4. Statistics the number of connections by user grouping

SELECT user, COUNT(*) as connections 
FROM information_schema.processlist 
GROUP BY user;

5. Check the number of connections usage

SELECT 
  (SELECT VARIABLE_VALUE 
   FROM performance_schema.global_status 
   WHERE VARIABLE_NAME = 'Threads_connected') AS current_connections,
  
  (SELECT VARIABLE_VALUE 
   FROM performance_schema.global_variables 
   WHERE VARIABLE_NAME = 'max_connections') AS max_connections,
  
  ROUND((SELECT VARIABLE_VALUE 
         FROM performance_schema.global_status 
         WHERE VARIABLE_NAME = 'Threads_connected') / 
        (SELECT VARIABLE_VALUE 
         FROM performance_schema.global_variables 
         WHERE VARIABLE_NAME = 'max_connections') * 100, 2) AS connection_usage_rate;

6. Check the number of connections in different states

SELECT command, COUNT(*) 
FROM information_schema.processlist 
GROUP BY command;

7. Check the number of idle connections (Sleep status)

SELECT COUNT(*) 
FROM information_schema.processlist 
WHERE command = 'Sleep';

Notes:

Requires at least PROCESS permission to view all connections
When the number of connections in the production environment is close to max_connections, it needs to be expanded or optimized.
For long-term Sleep connections, you can consider appropriately lowering them.wait_timeoutParameters

If you need to terminate the connection, you can use:

KILL [connection_id];  -- fromSHOW PROCESSLISTObtained in the resultsID