title: Database- Relational Algebra natural joins 2 tables consist 2 same column names
body: <p><a href="https://i.stack.imgur.com/jgcWJ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jgcWJ.png" alt="natural joins 2 relations"></a></p>
  
  <p>I have read through an example of <code>Natural Join</code> involving 2 relations that have 2 identical columns name. I understand those with 1 identical columns name in 2 tables, but really no idea about for this case. 
  Could anyone explain to me how to get that output (not in Sql command)?</p>
  
  <p>Thanks!</p>