title: How to determine the functional dependencies
body: <p>I am currently working for a University project and I'm a little bit confused now about the functional dependencies part. For this project I had to create a logical data model based on my own project specification and also determine the functional dependencies.</p>
  
  <p>For example, I have given the 'User' table the following attributes. <br />
  <strong>R(user_id, username, regDate, type, subscription)</strong> </p>
  
  <p><strong>Primary key:</strong> user_id <br />
  <strong>Unique key:</strong> username <br />
  <strong>Foreign key:</strong> subscription</p>
  
  <p>An example data set could be something like:</p>
  
  <blockquote>
    <p>1, JohnS, 01-01-2012, Administrator, NULL<br />
    2, PeterB, 02-01-2012, Moderator, Movies<br />
    3, PeterA, 02-01-2012, User, Movies<br />
    4, Gary, 03-01-2012, User, Books<br />
    5, Irene, 03-01-2012, User, Movies<br />
    6, Stan, 03-01-2012, User, Movies<br />
    7, Isaac, 04-01-2012, User, Books</p>
  </blockquote>
  
  <p>The part I don't understand is how I determine the functional dependencies. My initial feeling was that there are two functional dependencies and these are:<br />
  <strong>user_id -> username, regDate, type, subscription</strong> <br />
  <strong>username -> user_id, regDate, type, subscription</strong></p>
  
  <p>However, looking at the other examples in the lecture slides, I am having doubts whether this is correct or not.</p>