title: Neo4J Unicity wonders : singleton or aggregation issue
body: <p>I'm new to Neo4J and have a question for you guys.
  I import a CSV file and it duplicates my nodes instead of merging them.</p>
  <p><strong>Example</strong></p>
  <p>CSV FILE :</p>
  <pre><code>Id1,Id2,Relation
  Alice,Bob,KNOWS
  Morgane,Bob,KNOWS
  Bob,James,KNOWS
  </code></pre>
  <p>I would like to have a result as such</p>
  <pre><code>Alice---(KNOWS)---&gt;Bob&lt;---(KNOWS)---Morgane
                        ^
                        |
                    (KNOWS)
                        |
                      James
  
  </code></pre>
  <p>Though what happens is :</p>
  <pre><code>Alice---(KNOWS)---&gt;Bob
  Morgane---(KNOWS)---&gt;Bob
  Bob---(KNOWS)---&gt;James
  </code></pre>
  <p>I would like Bob to be a singleton, but it I get multiple &quot;Bob&quot; with different inner id's. I would like to merge all the Bobs together.
  Anyone have an idea ?</p>
  <p><em>(Note that the arrow between James &amp; Bob should be the otherway around on the &quot;wanted result&quot;, but it's ok, it's not so much the problem here)</em></p>
  <p>edit : I tried creating a constraint before importing the data, but it doesn't seem to be working :
  <code>CREATE CONSTRAINT ON (a:Person) ASSERT a.name IS UNIQUE;</code></p>
  <p>Thanks for your help !</p>