2. (12 pts). Circle ALL of the correct answers from the given choices (there may

Question

2. (12 pts). Circle ALL of the correct answers from the given choices (there may be more than one correct answers).

1) Unary (recursive) relationship type (3 pts)

a. Employees supervise multiple employees

b. Employees manage departments

c. A sales representative can back up another sales representative

d. Employees can works on multiple projects

e. None of the above

2) Strong and Weak entity type (3 pts)

a. Employee and Dependent entity types

b. College and Department entity types

c. Automobile and Part entity types

d. Course and Section entity types

e. None of the above

3) Single valued vs Multivalued attributes (3 pts)

a. Age vs Birth date (of Employee Entity type)

b. Employee_id vs Last_name (of Employee Entity type)

c. Account_Type vs Balance (of bank account)

d. Product_Number vs Product_Name (of Product Entity type)

e. None of the above

4) Simple vs. Composite attributes (3 pts)

a. Zip-Code vs Address (of Student Entity type)

b. First_name vs Full_name (of Employee Entity type)

c. Project_Number vs Project_Location (of Project Entity type)

d. Age vs. Birth Date

Explanation / Answer

(1) Unary relationship: Also known as one-to-one relationship ( it can be one-sided or two-sided).

Answer: (c) A sales representative can back up another sales representative and vice- versa.

(2) Strong and weak entity type:

Weak entity: An entity that does not have a primary key.

Strong entity: Weak entity is fully functionally dependent on strong entity. A weak entity is related via one-to-many relationship with a strong entity.

Answer: Here all (a),(b),(c),(d) are correct.

(a) For employee, employee number can be a primary key and its dependents are weak entity.

(b) For college, college number can be a primary key and department entities are weak entity types.

(c) For automobile, automobile number can be a primary key and parts are weak entity types.

(d) For course, course number can be a primary key and sections are weak entity types.

(3) Single valued v/s Multi valued attributes:

Answer: (c) Account type v/s balance.

Here, one type of account can have different balance.

(4) Simple v/s composite attributes.

Simple attribute: An attribute that is atomic in nature is a simple attribute.

Composite attribute: Attribute consisting of one or more simple attribute is a composite attribute.

Answer: (b) and (d)

(b) First_name vs Full_name:

First name is simple consisting only one name, Fullname can be subdivided into firstname and surname. Hence, it is composite in nature.

(d) Age is atomic in nature. Hence, it is simple attribute.

Birth date is composed of day, month and year. Hence, it is composite in nature.

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