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Chapter 7: Problem 23

A birthdate attribute would appear for many entity types – for example students, employees, children. What is a birthdate likely to be: key or non- key?

Short Answer

Expert verified
A birthdate is likely to be a non-key attribute because it does not uniquely identify every record, as different entities can have the same birthdate.

Step by step solution

01

Identify attributes

Define what key and non-key attributes are. A key attribute is a unique identifier for a record in a database. However, a non-key attribute is a feature that does not uniquely identify a record.
02

Analyze the given attribute

In this case, the attribute is 'birthdate'. There are many possible scenarios where two or more students, employees, or children (entities in general) could share a birthdate. Therefore, a birthdate doesn't necessarily uniquely identify a record, as multiple entities can have the same birthdate.
03

Determine if birthdate is a key or non-key attribute

Considering there can be repetitions in the 'birthdate' attribute among entities and it doesn't uniquely identify every entity, the 'birthdate' attribute should be considered as a non-key attribute.

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Most popular questions from this chapter

Assuming you have experience with some database system, what data type would you use for surrogate keys?

Consider a library and the fact that books are loaned out to library members. Dates could be used heavily for the date a book was borrowed, the date the book was returned, and the due date for a book. Consider an entity type Loan that has attributes book identifier, member identifier, date borrowed, date due, date returned. What combination of attributes would be a key? Which attributes are key attributes? Which attributes are non-key attributes?

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