title: Can SQLite support this schema?
body: <p>imagine I have this table called Department. Each Department can have child Departments.</p>
  
  <p>I was thinking of having a column called ParentDepartmentID as foreign key to another department. If this key is null, it means it's a Parent top class department and not child of any other department.</p>
  
  <p>I guess you could call this a self referencing ID. Does SQLite support this? Having a foreign key, but also allowing nulls?</p>
  
  <p>How would you solve this use case?</p>