22. The computer storage medium as recited in claim 21 , further comprising code for prompting a user to select preferences to be used during tuning based on whether the database query includes at least one of a NOT EXISTS, a NOT IN and an ALL clause.
22. The computer storage medium as recited in claim 21 , further comprising code for prompting a user to select preferences to be used during tuning based on whether the database query includes at least one of a NOT EXISTS, a NOT IN and an ALL clause. 23. The computer storage medium as recited in claim 22 , wherein the preferences include rewrite preferences for enabling a user to select at least one of a conversion of NOT EXISTS operators to a NOT IN operator and conversion of the selected database query to an outer join.