Consider the following table in a relational database Last Name Rank Room…
2018
Consider the following table in a relational database
Last Name Rank Room Shift
Smith Manager 234 Morning
Jones Custodian 33 Afternoon
Smith Custodian 33 Evening
Doe Clerical 222 Morning
According to the data shown in the table, which of the following could be a candidate key of the table?
- A.
{Last Name}
- B.
{Room}
- C.
{Shift}
- D.
{Room, Shift}
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Correct answer: D
A candidate key must uniquely identify every row in a table. In the given data, individual attributes like Last Name or Room contain duplicates across rows. However, the combination of Room and Shift produces a unique value for each row (e.g., 33/Afternoon is distinct from 33/Evening). Since {Room, Shift} ensures uniqueness for all entries, it qualifies as a candidate key.
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