The obvious answer to this one is have two separate logins/passwords - one 'user', one administator. Where MySQL comes into the equation I'm really not sure, unless you mean "a means to store the passwords", which could be done in all sots of ways.

I don't think anyone's yet clear on what kind of system you're talking about...a CGI script? An internal network application? A single box?. A little clarification could go a long way....

Ben.