Using the Entity Relationship Diagram you have drawn on your piece of paper for the Hamilton Island 'BoatRaceResults' Table, answer the following question.

Which would be the best choice for a primary key of the BoatRaceResults table?

Question

Using the Entity Relationship Diagram you have drawn  on your piece of paper for the Hamilton Island 'BoatRaceResults' Table, answer the following question.

Which would be the best choice for a primary key of the BoatRaceResults table?

BlackTom AI · Accepted Answer

First, let's restate the situation and the options to be evaluated. The BoatRaceResults table has rows that represent a boat's result in a given race, with attributes such as RaceID, BoatName, BoatSaleNum, Skipper, Place, RaceClass, RaceDate, etc. The question asks for the best choice of a primary key for this table.

Option 1: BoatClub
- Using BoatClub as a primary key would be problematic. Multiple boats can belong to the same club, and a single club will appear in many rows across different boats and races. This would not guarantee uniqueness for each row, violating the primary key requirement.

Option 2: RaceID, BoatName
- This combination likely uniquely identifies a specific boat’s entry in a particular race: the same RaceID can appear with multiple BoatName values (one per boat in that race), and the same BoatName can participate in multiple races with different RaceIDs. Together, RaceID and BoatName should uniquely identify each row, matching the real-world scenario of “this boat in this race.”

Option 3: RaceDate, BoatSaleNum
- RaceDate is not unique to a race itself (there can be multiple races on the same date in different contexts), and BoatSaleNum is not guaranteed to be unique across boats or races. This pair would likely fail to uniquely identify a row, leading to duplicates.

Option 4: RaceID
- RaceID alone identifies the race, but since many boats participate in a single race, RaceID would map to multiple rows. Therefore, RaceID by itself cannot serve as a primary key for a table that contains one row per boat in each race.

Putting these observations together, the only option that provides a unique identifier for each BoatRaceResults record is the composite key of RaceID and BoatName, which together ensure each row corresponds to a specific boat in a specific race.

Thus, the best choice for the primary key is RaceID, BoatName.

Using the Entity Relationship Diagram you have drawn on your piece of paper for the Hamilton Island 'BoatRaceResults' Table, answer the following question. Which would be the best choice for a primary key of the BoatRaceResults table?

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