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\subsection{Join Query Execution Plans}  Consider query   \textbf{SELECT \begin{verbatim}  SELECT  * FROM A \\}  \textbf{JOIN JOIN  B ON A.ID = B.ID \\}  \textbf{JOIN JOIN  C ON A.ID = C.ID \\}  \textbf{JOIN JOIN  D ON A.ID = D.ID \\} \end{verbatim}    Two possible execution plans are deep-left tree (shown in Figure-1 ) and Bushy Tree (shown in Figure-2). Other possible structures include right-deep trees zig-zag trees. Similar to deep-left trees right-deep and zig-zag are linear tree structure. But bushy trees are different and more complicated compared to others.