title: Does Postgresql SERIAL work differently?
body: <p>I have a postgres table with a SERIAL id. </p>
  
  <pre><code>id (serial) name age
  </code></pre>
  
  <p>Insert usually happens from a web application.</p>
  
  <p><em>I inserted manually two new records setting the id as max (id)+1</em>****</p>
  
  <p>After these 2 insert when the web app inserts 2 record it gives duplicate key error.</p>
  
  <p>Just for 2 records. After that everything works fine.</p>
  
  <p>The question is - Why didn't my manual insert increment the serial?</p>
  
  <p>Are auto increment and serial are different?</p>
  
  <p>What am I missing here? Do MySQL or any other SQL have the same issue?</p>