title: how to add composite unique to a column in the table mysql
body: <p>I have a table:</p>
  
  <ol>
  <li><code>user_id           int  Composite Unique (deal_id + user_id+deal_type)</code>.</li>
  <li><code>deal_id           int</code></li>
  <li><code>deal_type         varchar</code>.</li>
  <li><code>created_on        datetime</code>.</li>
  </ol>
  
  <p>This is my table. I want to create a composite unique on the <code>user_id</code> column so that a single user can have only unique <code>deal_id</code> for each <code>deal_type</code>. </p>
  
  <p>How to make composite unique for <strong><em>in mysql phpmyadmin</em></strong>.</p>