projecting functional dependencies onto another relation
<p>consider the relation <code>R(ABCDE)</code> with the following FD's:</p>

<ul>
<li>AB -> C</li>
<li>BC -> D</li>
<li>CD -> E</li>
<li>DE -> A</li>
<li>AE -> B</li>
</ul>

<p>Project these FD's onto the relation of <code>S(ABCD)</code>. Which of the following FD's hold in the projected relation? </p>

<ol>
<li>A -> B</li>
<li>A -> D</li>
<li>BC -> A</li>
<li>AC -> B</li>
</ol>

<p><em>the wording in the above question is directly copied from an assignment</em></p>

<p>The correct answer is given to be 3.</p>

<p>since the last 3 FD's contain E they do not hold in the projection onto R(ABCD) I believe. So that leaves me with
<code>AB -&gt; C</code> and <code>BC -&gt; D</code> I can not figure out how to determine the correct answer from my current though process.</p>