title: Comparing two rows in the same table SQL
body: <p>We are having trouble solving a part of an exercise in a SQL-course, here is a part of the dataset: <a href="https://i.stack.imgur.com/2fL7Q.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2fL7Q.png" alt="enter image description here" /></a></p>
  <p>The query we are looking for should: Find the diseases that can be treated with hydrocortisone but not with etanercept.</p>
  <p>Any ideas?</p>