How can I set the individual username, password for each site ?

I'm still fresh with Mysql, pls advise me.
Suppose I have 2 domins in my host such www.aa.com and www.bb.com . And now I've connected them with the same user and password (Admin Password).
But I would like to use the individual password and username for each domain, Because I've afraid of the big mistake. If there is someone know the admin's password, may he will destroy all databases that I have.
Could you let me know how I can create individual username and password for each domain ?

I've tried to find the information in this case but I still failed. Could you explain and give me a bit example?
Thank you very much.

grant all on database.* to user@localhost identified by 'password';

so it would be something like

grant all on aadb.* to aauser@localhost identified by 'aapass';

grant all on bbdb.* to bbuser@localhost identified by 'bbpass';

That should do it

Regards
Darren
http://www.php4hosting.com/ $ http://www.php4hosting.co.uk/ £

Yeh!! successfully...
Thank you very much for your knidness.