Union will provide the best performance and will then execute that strategy. Note: There is a major tradeoff for a DBMS when it comes to query optimization. Picking the most efficient query strategy can result in the shortest query execution time, but it is also possible for the DBMS to spend so much time figuring out which strategy is best that it consumes any performance advantage that might be had by executing the best strategy. Therefore, the query strat- egy used by a DBMS may not be the theoretically most efficient strategy, but it is the most efficient strategy that can be identified relatively quickly. The union operation creates a new table by placing all rows 37 Union