I'm currently building my application and populating it with data which currently stands at a few thousand rows and will eventually grow by a few thousand more.  My question is that eventually I'm going to move this into a sustaining phase and will be trying to engage with external users to update data based on the company they work for. 

      My goal is to limit view access based on organisation(s) or maybe an organisation and country. These are all currently captured in the database. I can see that the ability to view records appears to be limitable based on userr login, but as said before I've created the rows which I'm guessing will mean that won't be an option. Can I set something up which basically matches the user logging in to a table which contains the relevant authorizations for my database ? If possible can somebody give me a pointer 

Many Thanks

Simon