Query the running connections

SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST WHERE User='[username]';
-- or
SHOW PROCESSLIST;

Kill the running connecctions

SELECT CONCAT('KILL ', ID, ';') FROM INFORMATION_SCHEMA.PROCESSLIST WHERE User='[username]';

Get the max_user_connections setting of a user

SELECT max_user_connections FROM mysql.user WHERE User='[username]';

Create user

CREATE USER 'username'@'host' IDENTIFIED BY 'password';

Grant permission to a user

GRANT ALL ON *.* TO 'username'@'host' WITH GRANT OPTION;
FLUSH PRIVILEGES;

Grant permission to a database

GRANT ALL ON db1.* TO 'jeffrey'@'localhost'; 

Show created procedures

SHOW PROCEDURE STATUS;

Check permission of a DB user

SHOW GRANT FOR 'username'@'hostname';