title: ORA-00936: missing expression (sql-oracle)
body: <p><strong>I want to add 100 dollars to the old money, But tell me ORA-00936: missing expression</strong></p>
  
  <pre><code>create table sala(
      salary char(4));
  
  insert into sala values(300);
  
  
  create or replace trigger update_sal
  after insert on sala
  for each row
  when(new.salary in not null)
  begin
      update sala set salary=new.salary + 100;
  end;
  
  
  </code></pre>