title: id auto_inc column, but no primary key?
body: <p>I apologize for the bad title, but I wasn't sure how else to phrase it.</p>
  <p>Let's imagine for a moment that I wanted to create a <code>us_states</code> table as follow:</p>
  <pre class="lang-sql prettyprint-override"><code>create table us_states
  (
      id   serial,
      name varchar(256) not null constraint us_states_pk primary key,
      code varchar(256) not null
  );
  </code></pre>
  <p>What tangible benefits, if any, are there to having an auto incremental id column in a db_table if I don't plan on leveraging it as the primary key for said db_table?</p>