email password and username

I am trying to create a system where a user can retreive there user name and password details. The problem is that the user name /password is in one table and the contact details are in another. The contact details are refrenced to the username. I want to acheive the following: 1. A user enters their email address into a form 2. The form submits to the database 3. The form checks the email and picks up the username / password 4. An email is sent to the relevant address with the password details Can this be done? If so how?? Any comments will be grateful