I'm trying to create a web application for a dental laboratory where admins and clients, all users, can log-in and access to some specific data accordingly to their rol. Admins can create, modify and delete data, clients can only check information about their debts and purchases. My question is: Should I store all users, that's admins and customers, in a single table? or should I isolate them by creating two tables for each specific rol and set a in the log-in form where they can pick to log-in as customers or admins? It affects the overall performance somehow? Thanks.
You should use single table for all the users.
And for distinguishing admin and client you can add one extra column in the table which specify whether user is admin or client.