Find what the user group ID of Administrator group is by running:

SELECT user_group_id FROM user_groups WHERE context_id=0 AND role_id=1;

It’ll probably give a 1 back as a result. Then, you can grant that to user:

INSERT INTO user_user_groups (user_id, user_group_id) VALUES (278, 1);

where 278 is the user ID, and 1 is the user_group_id.

Reset admin password

UPDATE users SET password=SHA1(CONCAT(username,'w6Jdib4nNCZ')) WHERE username='admin';