Return all nodes in many-to-many hierarchal tree

Question

Similar to this question: How do I query for all the nodes between two nodes in a tree?

But I do not have a closure (flattened) table, a child can have many par

Answer 1

Since you need to model data where nodes can have multiple parents, a nested set/MPTT solution will not work. Another alternative is the use of a closure table.

You would create an additional table that held pairs of items for every ancestor's descendant (and vice versa):

AncID  DesID
  1      2
  1      6
  1      4
  1      8
  1      7
  1      3
  1      5
  1      9
  2      4
  2      8
  2      3
  2      5
  2      9
  4      3
  4      5
  4      9
  3      5
  3      9
  6      7

Then you would use a join to get the items you need:

SELECT * 
FROM Tbl INNER JOIN Closure ON Tbl.ID=Closure.DesID 
WHERE Closure.AncID = 2