here is how you could go about the two tasks:
- Query HOLDEVENT twice, so you get records with an event, an organizing club and another organizing club. Think of a way not to get both event = “Event 1” | club1 = “Club A” | club2 = “Club B” and event = “Event 1” | club1 = “Club B” | club2 = “Club A”. Then group by club1 and club2 and filter such that you get only those pairs having organized more than five events.
- Count the semesters each student was member since 1990. Compare to the actual number of semesters since 1990.
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solved How to query in Oracle [closed]