title: Expressing relational calculus & algebra queries in plain English re passengers, flights & trips in economy
body: <p>I have this statement:</p>
  
  <blockquote>
    <p><img src="https://i.stack.imgur.com/qXWrq.png" alt="enter image description here"></p>
  </blockquote>
  
  <p>And this one:</p>
  
  <blockquote>
    <p><img src="https://i.stack.imgur.com/tpz3Z.png" alt="enter image description here"></p>
  </blockquote>
  
  <p>How do I go about converting these to plain English?</p>
  
  <p>Here is the extent of my understanding:</p>
  
  <p>For the first one, I think it's selecting <strong>p_id</strong> where there exists <strong>f_no1</strong>, <strong>f_date</strong> and <strong>f_no2</strong> from the <strong>Flight</strong> and <strong>Trip</strong> tables joined.</p>
  
  <p>The second one is confusing; I know kind of what it's doing but I dont know how to convert it to plain English. It's natural joining the trip, flight and passenger tables, then it's selecting the rows from that resulting table where the class is business. From the rows where the class is business, it is then selecting only the rows where the final destination is Los Angeles, and then from those rows, it is selecting the passenger id and name. So I guess the English translation will be something along the lines of "Get the name and id of passengers going to Los Angeles in business class" but I'm not sure.</p>