title: SQL trigger for expiration date
body: <p>I have a table with the columns <code>expiration_date</code> and <code>isExpired</code>. I want to create a trigger to set the column <code>isExpired</code> to 1 if the column <code>expiration_date</code> passes the current date.</p>
  
  <p>I have no experience with triggers.</p>