An alternate way for obtaining a description of a tree that shows the paths
that can be used to reach vertices can be obtained using two pseudo-attributes
CONNECT BY ISLEAF and SYS CONNECT BY PATH. CONNECT BY LEAF returns 1 if
the current vertex, (in our case, the destination) of the edge is a leaf and 0,
otherwise.
For every edge of the path that joins the starting vertex to the current
node the pseudo-attribute SYS CONNECT BY PATH computes a string specified by
its first argument; entries between successive edges are separated by the string
specified by its second argument.
Example 5.20.8 The query: