title: Subtraction between two queries
body: <p>Let's say I have 2 database tables:</p>
  
  <p><code>table B</code> is a set of people, <code>table A</code> is a set of people from <code>table B</code> </p>
  
  <pre><code>Table A = (no, id, date) no is PK, id refer to table B
  
  Table B = (id, name) id is PK
  </code></pre>
  
  <p>My goal is to <strong>get data of people (id and name) who didn't attend on a given date</strong> (like today for example) the theory seems simple, set of B substract by set of A who attend (in today) but how can I do this in SQL query? I think about first query substracted by second query but got confused.</p>