title: A self join query
body: <p>Given this relational schema</p>
  <ul>
  <li>people (pid, name, gender, age, email, city, state)</li>
  <li>books (ISBN, title, edition, publisher, year, rating)</li>
  <li>write (pid, ISBN) pid is a foreign key and refers to people (pid), ISBN is a foreign key and refers to books (ISBN)</li>
  </ul>
  <p>I need to write a SQL query to find the authors who either never published co-authored books or only co-authored with others from the same state, return their names.</p>
  <p>I know I need to use a self join but not sure how to do that.</p>
  <p>Thanks!</p>