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\subsection{Challenegs in Bushy Tree Implementation}  Moving from left-deep tree to a Bushy tree is a challenge as the number of possible structures in bushy trees are much larger. On the other hand left-deep trees have only one structure regardless of the number of tables involved. Therefor the number of possible permutations are N!. But for bushy trees possible number of structures is given by,\\ by,  $$ $S(N) = \displaystyle \sum_{N=1}^{i} (N)(N-i)$ \ $ for N > 1$ $$\\