Get data from two tables with recursive relationships
BAD NEWS

MySQL does not support recursive data or table structures. Neither does it support recursive SQL.

GOOD NEWS

There is a hope. I have written some stored functions on how to retrieve hierarchies of data


Oct 24, 2011 : Find highest level of a hierarchical field: with vs without CTEs 
Dec 10, 2012 : MySQL: Tree-Hierarchical query


CAVEAT


You would have to implement this against your tables.
You also need to make sure you are entering data as a Tree and not as a Graph.


https://en.wikipedia.org/wiki/Tree_(data_structure)
http://wiki.answers.com/Q/DIFFERENCE_between_GRAPH_and_TREE_IN_DATA_STRUCTURES
https://stackoverflow.com/a/7707983/491757

For any row in the position_inherits table that does not have a parent, simply set that row's inherit_privs_from to zero(0). That way, you have establish root positions.