The solution I provided might help. But, as said by other posters, the data structure is required. I posted on my assumption that;

B is descendent of A

E and F are Decendents of B

C is decendent of A

and

D is decendent of C

Now asuming this, I understood that if the OP queries B, he/she needs to get the complete hirarchy from B and its decendents and its decendents' decendents and so on....

I hope the same thing was required...