title: Why does Oracle pseudo column CONNECT_BY_ISLEAF seems broken?
body: <h1>First a short description of my Issue</h1>
  
  <p>I have a table containing data which may be represented in this pseudo directed graph:
  <a href="https://i.stack.imgur.com/PmidT.png" rel="noreferrer" title="Pseudo directed graph datas"><img src="https://i.stack.imgur.com/PmidT.png" alt="Pseudo-graph image" title="Pseudo directed graph datas"></a>
  I say it is a pseudo-graph because I have some «edges» which are only connected on 1 node.</p>
  
  <p>Each «edges» are labelled, and will be refereed to as an event.</p>
  
  <p>Each nodes contain only one ID.</p>
  
  <p>The Oracle (12c) table look like this:
  <a href="http://sqlfiddle.com/#!4/79cdb5/4/0" rel="noreferrer">http://sqlfiddle.com/#!4/79cdb5/4/0</a></p>
  
  <p>on the Table I ran <a href="http://sqlfiddle.com/#!4/79cdb5/2/1" rel="noreferrer">this query</a>
  and one of the row I expected to have a 1 in its pseudo column CONNECT_BY_ISLEAF has instead a 0.</p>
  
  <p>This is the guilty row:
  <a href="http://sqlfiddle.com/#!4/79cdb5/3/2" rel="noreferrer">http://sqlfiddle.com/#!4/79cdb5/3/2</a></p>
  
  <p>I am completely unable to understand why oracle does not consider this row to be a leaf when it obviously is one.</p>
  
  <h1>Description of the table data</h1>
  
  <p>In the table I am using each row represent an event (or graph edge) plus the node(s) to which it is connected.</p>
  
  <p>the VUID column is the “previous” node, the AUID is «step», the EVENT is the event label, the NEW_VUID is the “next” node.</p>
  
  <p>Exception is for event D and U which only have 1 node connected to it and this node will always be in the VUID column (even if for D event the node is the “next” node).</p>
  
  <h3>Description and aim of the faulty request</h3>
  
  <p>Here I will just give some context about the request I am doing</p>
  
  <p>My final aim is to recreate this graph based on the data there is in the Table.
  For that I proceed in steps:</p>
  
  <ol>
  <li>Build the «forward» trees, each root must be node with a D «edge»</li>
  <li>Build the «reverse» tree, each root would be node with no child</li>
  <li>«merge» all the relevant trees together to end up with the wanted graph. Final graph should be close to the one shown at beginning of this question. </li>
  </ol>
  
  <p>During step 1. I should end up with forward trees looking like that:
  <a href="https://i.stack.imgur.com/tJpFk.png" rel="noreferrer" title="First forward tree"><img src="https://i.stack.imgur.com/tJpFk.png" alt="First computed forward tree" title="First forward tree"></a>
  <a href="https://i.stack.imgur.com/SaQJg.png" rel="noreferrer" title="Second forward tree"><img src="https://i.stack.imgur.com/SaQJg.png" alt="Second computed forward tree" title="Second forward tree"></a></p>
  
  <p>To create the trees with oracle I think the easiest would be to make the right hierarchical query and then use the pseudo column SYS_CONNECT_BY_PATH and filter on CONNECT_BY_ISLEAF = 1, this is because using only leaf plus the path each leaf had it is easy to re-create the tree.</p>
  
  <p>However I am stuck because for some reason I do not understand Oracle is not considering all leaf the same way I do.
  The leaf containing the node 88888 is not considering </p>