title: Basic configuration of database permissions
body: <p>I'm learning databases and I have a question how to prepare the rules and groups configuration for the following assumptions:</p>
  
  <p>I have two databases:</p>
  
  <ul>
  <li>databaseA </li>
  <li>databaseB</li>
  </ul>
  
  <p>Each database will have several users connecting using the connectionString (server, port, database, username, password). So I have 3 users to each database:</p>
  
  <ul>
  <li>userA1, userA2, userA3</li>
  <li>userB1, userB2, userB3</li>
  </ul>
  
  <p>How to create groups and roles and how to grant permission so that users A can only connect to database A and users B to database B. Can I make A users not see database B, have not seen users assigned to database B?</p>
  
  <p>Probably it is a simple question, but I would like to see an example of how to do it - for now I have A and B database and the <code>postgres</code> user.</p>