title: How to store multiple values in single column where use less memory?
body: <p>I have a table of <em>users</em> where 1 column stores user's "roles".
  We can assign <em>multiple roles</em> to particular user.</p>
  
  <p>Then I want to store role IDs in the "roles" column.</p>
  
  <p>But how can I store multiple values into a single column to save memory in a way that is easy to use? For example, storing using a comma-delimited field is not easy and uses memory.</p>
  
  <p>Any ideas?</p>