title: PostgreSQL - create an auto-increment column for non-primary key
body: <p>I am with PostgreSQL 9.5 X64 integrated with the open-source Parse Server. My table has the following structure.</p>
  
  <pre><code>objectId (text with fixed 10 characters),
  item_id (integer),
  item_name (text with various length)
  </code></pre>
  
  <p>The <code>objectId</code> is the primary key due to use of Parse Server. It is automatically generated by Parse Server. The <code>item_id</code> is not a primary key. I would like to have <code>item_id</code> automatically increment by 1 when a new record is created. How can this be achieved in Create Table?</p>