An index on cid in Competes will speed query (Y).
This index will hasten query (X)
Neither of the queries mentioned would use such an index.
Such an index would expedite query (X).
The execution of query (Y) would be accelerated by such an index.
An athletics meeting involves several competitors who participate in a number of events. The database is intended to record who is to take part in which event and to record the outcome of each event. As results become available the winner attribute will be updated with the cid of the appropriate competitor.
Competitor(cid, name, nationality) Event(eid, description, winner) Competes(cid, eid)
The actual database is to contain several million competitors and nearly one hundred thousand events. The database must be indexed for producing fast results for two particular queries:
Which of the following is not required?