title: Superkey, candidate key & primary key
body: <p>Can any kind soul clarify my doubts with a simple example below and identify the superkey, candidate key and primary key?</p>
  
  <p>I know there are a lot of posts and websites out there explaining the differences between them. But it looks like all are generic definitions.</p>
  
  <p>Example:</p>
  
  <pre><code>Student (StudentNumber, FamilyName, Degree, Major, Grade, PhoneNumber)
  </code></pre>
  
  <p>So from the above example, I can know <code>StudentNumber</code> is a primary key.</p>
  
  <p>But as for superkey, I'm a bit confused what combination of attributes  could be grouped into the superkey?</p>
  
  <p>As for candidate key, I'm confused by the definition given as any candidate key can qualify as a primary key.</p>
  
  <p>Does it mean that attributes such as <code>PhoneNumber</code> are a candidate key and can be a primary key? (Assuming that a <code>PhoneNumber</code> only belongs to one student)  </p>
  
  <p>Thanks for any clarification!</p>