title: Postgresql: filter query to hide all from column a if any of column b has specific value
body: <p>I am new to postgresql/ sqlalchemy and I had a query question. I have the following join table </p>
  
  <pre><code>select classroom.name, student.class_name, student.full_name
  from classroom
  inner join student on classroom.name = student.class_name
  </code></pre>
  
  <p>Which returns the following:</p>
  
  <pre><code>classroom.name | student.class_name | student.full_name
  -------------------------------------------------------
  Math           |        Math        |        Joe
  Math           |        Math        |        Kim
  Math           |        Math        |       Chris
  English        |       English      |        Joe
  English        |       English      |        Kim
  </code></pre>
  
  <p>What I am trying to do is filter this query so that if a certain student, lets just Chris, exists in the student.name column, it wouldnt return any row with classroom.name = Math since one of the entries has Chris. So the output that I am looking for is </p>
  
  <pre><code>classroom.name | student.class_name | student.full_name
  -------------------------------------------------------
  English        |       English      |        Joe
  English        |       English      |        Kim
  </code></pre>
  
  <p>I've tried adding a <code>Where student.full_name = 'Chris'</code>, but that only hid the one entry and still left the other two entries. </p>
  
  <p>Any help would be appreciated, thank you!</p>