title: Queries without Aggregate or SubQuery
body: <p>I'm wondering if it is possible to find all instructors that teach 'Math' and does not teach 'English', <strong>without</strong> using aggregate <strong>or</strong> subqueries. </p>
  
  <p>My normal approach is to use subqueries/aggregates by finding all those that teach English and use: where instructor not in (select instructor from course where course = 'English') or to group by instructor, course having count(*) > 1. </p>
  
  <p>// Test Input and Output below</p>
  
  <pre><code>CREATE TABLE testTable (instructor TEXT, course TEXT);
  
  INSERT INTO testTable values ('John Doe', 'Math');
  
  INSERT INTO testTable values ('John Doe', 'English');
  
  INSERT INTO testTable values ('John Doe', 'Physics');
  
  INSERT INTO testTable values ('Jane Doe', 'Math');
  
  INSERT INTO testTable values ('John Smith', 'Physics');
  
  INSERT INTO testTable values ('John Smith', 'Math');
  
  INSERT INTO testTable values ('Janice Smith', 'English');
  </code></pre>
  
  <p>Solution should be:</p>
  
  <pre><code>Jane Doe
  
  John Smith
  </code></pre>