title: Understanding Functional Dependencies
body: <p>I'm currently learning about functional dependencies and am struggling to get my head around the concept behind them.</p>
  
  <p>Say I have the table:</p>
  
  <p><strong>Customer</strong></p>
  
  <pre><code>|-----------|--------------|------------|------------------|------------------|
  |Cust-ID    | Cust-FName   |Cust-LName  |Cust-Email        |Cust-Pw           |
  |-----------|--------------|------------|------------------|------------------|
  |1          |John          |Smith       |jsmith@email.com  |srt6564sdgjhy55y  |
  |2          |Adam          |Borneo      |adb@hotmail.com   |45657ythjdfgqAfd  |
  -------------------------------------------------------------------------------
  </code></pre>
  
  <p>There are two candidate keys: cust-ID and cust-Email (only one email address may belong to one customer). Electing cust-ID as the P.K, would the only functional dependency be:</p>
  
  <p><code>{Cust-ID} -&gt; {Cust-FName, Cust-LName, Cust-Email, Cust-Pw}</code> ?</p>
  
  <p>Or, would I draw/represent both candidate keys:</p>
  
  <p><code>{Cust-ID} -&gt; {Cust-FName, Cust-LName, Cust-Email, Cust-Pw}</code></p>
  
  <p><code>{Cust-Email} -&gt; {Cust-ID, Cust-FName, Cust-LName, Cust-Pw}</code> ?</p>
  
  <p>Instincts tell me the former, but given this is a completely new topic I'd appreciate any help!</p>