title: Unknown part of ER model
body: <p>I want to create this, but I have no idea how it really is. My guess is that maybe it works like a foreign key inside the table Employee, but again , I don't understand how can you create something like this. I am sorry if this is already been answered , but I have no idea how to search it.</p>
  
  <p><img src="https://i.stack.imgur.com/59bSz.png" alt="enter image description here"></p>