title: SQL: selecting the set of A not B
body: <p>I have Two tables: left one is users_projects, right one is projects:
  <a href="https://i.stack.imgur.com/PAH1e.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PAH1e.png" alt="enter image description here"></a></p>
  
  <p>I want to select the projects that user 3 is not participating in (only p_ID 5 and 7).</p>
  
  <p>I've tried <code>SELECT * FROM users_projects up INNER JOIN projects p ON p.p_ID=up.p_ID WHERE up.u_ID!=3</code></p>
  
  <p>but that also returns me p_ID 1 which both user 2 and 3 are a part of. </p>
  
  <p>Thanks for your help!</p>