Clients that access your database?
Client information in a client record that should be seen by a single group of users with database access?
HIPPA involved? (medical information)
The first 5 or 7 links are a start to explain your requirements a bit more.
You might also examine each of the script steps in the Account category. It's possible to set up a layout, scripts and a table for managing accounts, passwords and existing privilege sets. And by setting up scripts that run with full access privileges, this can be a system that is managed by someone to whom full access has not been granted.
The access is for each client to access it's own custom application. I need to set up the levels of access (granularity) for General Manger, Department Supervisor, data entry person and some of these should not have access to all files. With the exception of the data entry passwords, which must be set by each person, I set these up for each client. Lot's of work, not much fun. No HIPPA or other regulatory issues. Does the framework exist so I can buy it or must I reinvent the thing from scratch?