I've never worked with databases before.

Generally, is it better to GRANT each person registered to your site some basic privileges and when they log in connect to the database with their login/password, or else is it better to use the same login and password for each user using an account with broader database privileges (but not full privileges), and just verify users by querying a table using the login and password information they logged in with???

Which is more efficient?

Is there major problems with either situation?

Also, what is the general process for validating a users' login and password, with specifics if you can. Do you query a large table of different users looking for a login and password match??

Thanks, G