8. The method of claim 7 , wherein said generating step further comprises: generating a left deep nested loop join tree based on combining particular subplans covering all tables from which the query requests data.
7. The method of claim 1 , wherein said generating step includes substeps of: generating subplans structured as left deep nested loop join subtrees for obtaining data requested by the query; grouping said subplans into classes based on tables covered by each subplan; and for each class, selecting a particular subplan having favorable execution costs.