title: SharePoint 2013 REST How to $filter field1 eq field2 (not field eq constantValue)?
body: <p>Am I missing something or is it really impossible to use SharePoint REST API to filter a list based on the contents of a field and another field? </p>
  
  <p>Constant values work: </p>
  
  <pre><code>?$select=Title&amp;$filter=Title eq 'Hello world'
  </code></pre>
  
  <p>or</p>
  
  <pre><code>?$select=Title&amp;$filter='Hello world' eq Title
  </code></pre>
  
  <p>but <em>not</em></p>
  
  <pre><code>?$select=Title&amp;$filter=Title eq Title
  </code></pre>
  
  <p>nor </p>
  
  <pre><code>?$select=Title&amp;$filter=Title eq OtherField
  </code></pre>
  
  <p>nor</p>
  
  <pre><code>?$select=Title&amp;$filter=substringof(Title, Title)
  </code></pre>
  
  <p>With filtering that limited, REST is practically useless. </p>
  
  <p>Is there some way to use variables or refer to other fields? </p>
  
  <p><strong>EDIT:</strong>
  I just checked, apparently it is a limitation in the SharePoint. 
  It also does not work using CAML, apparently all comparisons have to be Field to ConstantValue. </p>
  
  <p>Doesn't work either: </p>
  
  <pre><code>&lt;Query&gt;
  &lt;Where&gt;&lt;Eq&gt;&lt;FieldRef Name="Title" /&gt;&lt;FieldRef Name="Title" /&gt;&lt;/Eq&gt;&lt;/Where&gt;
  &lt;/Query&gt;
  </code></pre>
  
  <p>Any idea how to work around this issue? Lookups, Joins? In REST? Thanks. </p>