title: Do I have to fill foreign key values?
body: <p>Do I have to fill the field of a foreign key in MySQL or any other database manager?.</p>
  
  <p>I'm writing the data of a table and when I get to the field that is a FK from another table, I have to write something, is this necessary?</p>
  
  <p>I understand that the value in that FK is stored inside the parent table where it comes from.</p>