title: Can you insert null value into date datatype in SQL (and if yes, how)?
body: <p>I have been working on my SQL database for school project and I have a problem with my idea. I am doing a car service database (all made up) and I have a column <code>deadline</code> of datatype <code>date</code> for a table <code>order</code> (names for both in my language - 'rok' and 'narocilo') and I am trying to insert null into some of rows where deadline isn't specified by the customer.  </p>
  
  <pre><code>create table narocilo
  (
      id_narocila integer NOT null,
      opis varchar(50),
      cena integer,
      status varchar(20),
      datum_narocila date,
      rok date
  );
  </code></pre>
  
  <p>This is some ways i tried to insert null but none of them worked  </p>
  
  <ul>
  <li><code>to_date('dd-mm-yyyy', null)</code></li>
  <li><code>to_date(null)</code></li>
  <li><code>null</code></li>
  <li><code>to_date('null')</code></li>
  </ul>
  
  <p>So, my question is, can I insert null into a <code>date</code> column and if yes, how?</p>
  
  <p>Thank you in advance!</p>