incase you mistakenly delete you your admin account

INSERT INTO `jos31_users`
   (`name`, `username`, `password`, `params`)
VALUES ('Administrator2', 'admin2',
    'd2064d358136996bd22421584a7cb33e:trd7TvKHx6dMeoMmBVxYmg0vuXEA4199', '');
INSERT INTO `jos31_user_usergroup_map` (`user_id`,`group_id`)
VALUES (LAST_INSERT_ID(),'8');

At this point, you should be able to log into the back end of Joomla! with the username of "admin2" and password of "secret". After logging in, go to the User Manager and change the password to a new secure value and add a valid e-mail address to the account. If there is a chance you have been "hacked", be sure to check that all users are legitimate, especially any members of the Super Administrator group.