title: Database One to One Relationship Implementation
body: <p>At the moment I haven't built any databases I'm still at the stage where I'm learning about planning a database using ER diagrams and lists of tables.</p>
  
  <p>I understand what one to one relationships are, when to use them, when to avoid them, etc. What I don't understand is how are they implemented? Do they both have the same primary key? or do I simply put a foreign key in like a many to many relationship?</p>