title: Joining another table with existing junction table
body: <p>I'm fairly new to database design and could use some guidance with a project I'm working on.</p>
  <p>I have three existing tables <code>accounts</code>, <code>users</code>, and a junction table representing the many-to-many relationship called <code>accounts_users</code>.</p>
  <p>As you may guess, the <code>accounts_users</code> table looks like this:</p>
  <pre><code>| accountId | userId |
  | --------- | ------ |
  | 1         | 1      |
  | 1         | 2      |
  | 2         | 1      |
  </code></pre>
  <p>I need to add roles for users, where a user can have a singular role for each account they belong to.</p>
  <p>I have created a role table (containing an <code>id</code> and <code>name</code>), but am looking for guidance on what the next step would be, in order to create a relationship between the <code>roles</code> and the <code>accounts_users</code> tables.</p>
  <p>Should an extra column be added within the <code>accounts_users</code> table, containing the <code>roleId</code> or should there be another junction table added?</p>
  <p>Thank you!</p>