title: What is the best way to store user notifications in MySQL?
body: <p>I am building a noticeboard module in a php/mysql app.  The idea is an admin can post notices to a single user, groups of users (by role), perhaps combinations of users/groups/roles, everyone in the system.</p>
  
  <p>My initial thoughts were to have the following schema which solves my send to a single user or single user role:</p>
  
  <pre><code>notices
  ----------------
  notice_id
  notice_date
  notice_title
  notice_text
  notice_recipients  &lt;-- linked to user_role_id (from user_roles table)
  </code></pre>
  
  <p>I'm not sure how to record 2 groups and/or 50 individual recipients without having duplicated rows in the database.  Is it possible to store all the <em>user_role_id</em>'s in the one <em>notice_recipients</em> field and then somehow read the contents of that field to display in each individual users noticeboard? </p>