title: Is it ok with entity-entity relationship in ER diagram?
body: <p>As the title says is it ok to have entity-entity relationships in ER diagrams?
  I'm designing a database for a sports competition and would like to have that "teams" belong to certain "sports" and that "event" are certain "sports".</p>
  
  <ol>
  <li>Teams((team_id), sport_id, country)</li>
  <li>Sports((sport_id), sport, sub_category) </li>
  <li>Event((event_id), sport_id, group)</li>
  </ol>
  
  <p>Or is it better to represent them with relationships between ? </p>