Looking to your question, I think that may be you will no be able to do what you want with Group Policies.
Restricting access to any database is *usually* done using the application that manages it. Configuring users, access levels, etc. that are allowed to access each part that . Ultimately, being for example an SQL database, with SQL Server logins, roles, but this might be a huge task.
You need to be more specific so we can provide a better answer.