How can I make a user access control without mysql (GRANT/REVOKE) but with phpmyadmin (write, read a.s.o.). I know that I have to create a table of users, a table of groups and a third table with groupId and userId.
Where can I get or who can give me some more information about it (not too theoretical)?
If I understand what you are saying, you basically want something like phpmyadmin, but without having to create users at the MySQL level with GRANT and REVOKE.
What you would need is some kind of control panel where they can run queries and such (or use other tools you could build). You would then control their login with a user table, which doesn't necessarily require other tables (but it's a good idea).
So, essentially you would be creating your own version of phpmyadmin, but you would be logging in using your own user table, and the queries are powered by one user login.