Oracle hierarchical query on non-hierarchical data

Question

I hava data in an Oracle table that is organized as a graph that can contain cycles (see example).

     CREATE TABLE T (parent INTEGER, child INTEGER)
                   


        

Answer 1

This might help until visited exceeds 4000 bytes. Cycles should not be possible but the line is there just as an example.

   WITH descendants(node, lvl, pth, visited) AS
    (
    SELECT child node, 1, cast(child as varchar2(4000)), '/'||listagg(child,'/') within group (order by child) over()||'/'
      FROM t 
     where parent = 2
     UNION ALL
    SELECT child, lvl+1, pth||'/'||child, D.visited||listagg(child,'/') within group (order by child) over()||'/'
      FROM T
     INNER JOIN descendants D
        ON T.parent = D.node
     WHERE D.visited not like '%/'||child||'/%'
    )
    cycle node set cyc to '1' default '0' 
    SELECT distinct node
      FROM descendants
     order by node
    ;