title: Entity Relationship Diagram. How does the IS A relationship translate into tables?
body: <p><img src="https://i.stack.imgur.com/GvSsF.jpg" alt="My drawing of a simple ER diagram"></p>
  
  <p>I was simply wondering, how an ISA relationship in an ER diagram would translate into tables in a database.  </p>
  
  <p>Would there be 3 tables?  One for person, one for student, and one for Teacher?</p>
  
  <p>Or would there be 2 tables?  One for student, and one for teacher, with each entity having the attributes of person + their own?</p>
  
  <p>Or would there be one table with all 4 attributes and some of the squares in the table being null depending on whether it was a student or teacher in the row?</p>
  
  <p>NOTE: I forgot to add this, but there is full coverage for the ISA relationship, so a person must be either a studen or a teacher.</p>