title: Best way to do fetching of row with attribute that is not referenced to other attribute in Core Data
body: <p>I have 1 entity called Project with attribute of:</p>
  
  <ul>
  <li>ProjectNo</li>
  <li>ProjectNoRef (reference to ProjectNo attribute)</li>
  <li>Month</li>
  </ul>
  
  <p>Example:</p>
  
  <pre><code>===================================
  | ProjectNo | ProjectNoRef| Month |
  ===================================
  |   Proj01  |     NULL    |   1   |
  |   Proj02  |     NULL    |   1   |
  |   Proj03  |     NULL    |   1   |
  |   Proj04  |     NULL    |   1   |
  |   Proj05  |    Proj01   |   2   |
  |   Proj06  |     NULL    |   2   |
  ===================================
  </code></pre>
  
  <p>I want to fetch all projects within certain month that is not referenced to other project.</p>
  
  <p>From above example, it will result 3 for month 1 and 2 for month 2.</p>
  
  <p>What is the best way to do this in Core Data? I don't want to do double fetching as there will be thousand projects.</p>