mysql改用户名和密码

ALTER USER 'old_username'@'localhost' IDENTIFIED BY 'new_password';

SET PASSWORD FOR 'old_username'@'localhost' = PASSWORD('new_password');

CREATE USER 'new_username'@'localhost' IDENTIFIED BY 'new_password';
GRANT ALL PRIVILEGES ON *.* TO 'new_username'@'localhost';
REVOKE ALL PRIVILEGES ON *.* FROM 'old_username'@'localhost';
DROP USER 'old_username'@'localhost';

CREATE USER 'new_username'@'localhost' IDENTIFIED BY 'new_password';
GRANT SELECT, INSERT, UPDATE ON database_name.* TO 'new_username'@'localhost';
FLUSH PRIVILEGES;

USE mysql;
UPDATE user SET authentication_string=PASSWORD('new_password') WHERE User='old_username';
FLUSH PRIVILEGES;

SELECT User FROM mysql.user WHERE User='old_username';

SHOW VARIABLES LIKE 'validate_password%';
SET GLOBAL validate_password_policy=LOW;