title: In ER diagram ,is it possible that primary key is not showing?why?
body: <p>here,i have seen diagram in which there is no primary key for entity.</p>
  
  <p>in this diagram,item's order_level and price has no primary key.if there is not primary key then it is how to show in data dictionary? 
  <img src="https://i.stack.imgur.com/zJLbv.png" alt=""></p>