Consider attributes ID, CITY and NAME. Which one of this can be considered as a super key?Question 2Answera.CITY, IDb.NAMEc.CITYd.ID
Question
Consider attributes ID, CITY and NAME. Which one of this can be considered as a super key?Question 2Answera.CITY, IDb.NAMEc.CITYd.ID
Solution
A super key is a set of one or more keys that can be used to uniquely identify a record in a table.
Looking at the attributes ID, CITY, and NAME, we can consider the following:
a. CITY, ID: This can be a super key because the combination of CITY and ID can uniquely identify a record. Different people (NAME) can live in the same city (CITY) and different people can have the same name (NAME), but no two people can have the same ID in the same city.
b. NAME: This cannot be a super key because names are not unique. More than one person can have the same name.
c. CITY: This cannot be a super key because cities are not unique. More than one person can live in the same city.
d. ID: This can be a super key because IDs are unique. No two people can have the same ID.
So, the possible super keys are CITY, ID and ID.
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