title: How can I change existing column as Identity in PostgreSQL 11.1
body: <p>I would like to changes my existing column as Auto Identity in a Postgres Database. <br>
  I tried with below script but it won't worked.<br>
  Let me know if you have solution for the same<br>
  I don't want to use postgres SEQUENCE. I would like to use <strong>GENERATED ALWAYS AS IDENTITY</strong>.</p>
  
  <pre><code>ALTER TABLE public.patient ALTER COLUMN patientid Type int4 
  USING patientid::int4 GENERATED ALWAYS AS IDENTITY;
  </code></pre>