title: If a row does not exists insert else don't insert in postgres
body: <p>I need to check if a row exists or not. If it does not exist, it should be inserted. </p>
  
  <p>This is in <code>postgres</code> and I am trying to insert row through a shell script. When I run the script it does not show error but it does not insert into table even though no matching row is present.</p>