Create a New User and Grant Permissions in MySQL

create/delete users 

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CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'password';

DROP USER ‘demo’@‘localhost’;

Change passwords

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mysqladmin -u USER -p password NEWPASSWORD

mysqladmin -u marcelo -p oLdpa$$word 'NEwP@$$'
mysql> use mysql;

SET PASSWORD FOR 'user-name-here'@'hostname-name-here' = PASSWORD('new-password-here');

flush privileges;

GRANTING/REVOKE PRIVILEGES

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GRANT ALL PRIVILEGES ON *.* TO 'newuser'@'localhost';

OR

GRANT ALL PRIVILEGES ON demoDB.* TO 'newuser'@'localhost';

GRANT SELECT,UPDATE,DELETE ON testDB.* TO 'demo-user'@'localhost';

REVOKE UPDATE ON testDB.* FROM 'demo-user'@'localhost';

GRANT ALL ON testDB.* TO 'demo-user'@'localhost';

FLUSH PRIVILEGES;

show grants for 'demo-user'@'localhost';

Privileges:-

= = = = = = 

ALL PRIVILEGES,CREATE,DROP,DELETE,INSERT,SELECT,UPDATE,GRANT OPTION

ALL PRIVILEGES- as we saw previously, this would allow a MySQL 
user all access to a designated database (or if no database is selected,
 across the system)
CREATE- allows them to create new tables or databases
DROP- allows them to them to delete tables or databases
DELETE- allows them to delete rows from tables 
INSERT- allows them to insert rows into tables
SELECT- allows them to use the Select command to read through databases
UPDATE- allow them to update table rows
GRANT OPTION- allows them to grant  or remove other users' privileges

To provide a specific user with a permission, you can use this framework:



 GRANT [type of permission] ON [database name].[table name] TO ‘[username]’@'localhost’;


The root login can be changed with the following command:
---------------------------------------------------------- 
rename user 'root'@'localhost' to 'newAdminUser'@'localhost';