Admin account lost admin rights

I have a strange Problem:

I have two accounts on a server (4.15), one was the admin account, the second one without admin rights. Now the admin account has no admin rights anymore, neither does the second account. So I cannot add new users, change user rights and so on. I have no idea when or how this has happend. Does somebody know, how to give the admin account its admin rights back?

Use sql to set the administrator bit on the user in tc_users.

update tc_users set administrator=1 where name="admin";

Thanks for the quick answer! Unfortunately, I am not familiar with direct SQL manipulation. Is your last post the exact command to be used in the database console window? The account to be set as administrator in my case is indeed named "admin"

Just figured it out on my own, thanks again! I only had to replace the quotation marks:

update tc_users set administrator=1 where name='admin';

worked like a charm in the web console.