SHOW STATUS LIKE 'Threads_connected';

SHOW VARIABLES LIKE 'max_connections';

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

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;

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

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

KILL [connection_id];  -- 从SHOW PROCESSLIST结果中获取ID