ACO 320: Final Exam Study Guide - Module 1, 2, and 3

1. Which statement is true regarding a relation?

• The tuples of a relation are ordered by the primary key.

• Every attribute in a tuple must have a value.

• Every tuple in a relation must be unique.

• An attribute name can occur more than once in a relation.

1. What term refers to a description of a relation?

• extension

• schema

• atomic

• instance

1. What notation correctly refers to the set of attributes in the title relation?

• title

• {tTitle, tMinSalary, tMaxSalary }

• TTitle

• (tTitle, tMinSalary, tMaxSalary)

1. Which statement is true regarding superkeys, candidate keys, and primary keys?

• A relation may not have a superkey.

• Every superkey is a primary key.

• Every candidate key is a primary key.

• A primary key is a superkey.

1. Based on the description of the title relation in the text, which choice represents a candidate key for the title relation?

• {tTitle }

• TITLE

• (tTitle)

• {tTitle, tMinSalary }

1. Which statement is true regarding primary and foreign keys?

• The non‐null value of a foreign key attribute must appear as a value of its referenced primary key.

• The non‐null value of a primary key attribute must appear as a value of its referencing foreign key.

• The value of a foreign key cannot be null.

• The value of a primary key can be null.

1. Which expression is true regarding the comparison of the set of distinct values of the title occurring in the relation employee(eID, eLast, eFirst, eTitle, eSalary) versus the relation title(tTitle, tMinSalary, tMaxSalary)?

• eTitle ≤ tTitle

• employee.eTitle ≤ title.tTitle

• employee.eTitle ⊇ title.tTitle

• employee.eTitle ⊆ title.tTitle

1. Which expression is most likely true regarding the cardinality of the relation employee(eID, eLast, eFirst, eTitle, eSalary) versus the cardinality of the relation title(tTitle, tMinSalary, tMaxSalary)?

• ∣ employee ∣ ⊇ ∣ title ∣

• ∣ employee ∣ ≥ ∣ title ∣

• ∣ employee ∣ ≤ ∣ title ∣

• ∣ employee.eID ∣ ≤ ∣ title.tTitle ∣

1. In the ONLINE RETAILER example, what does it mean when orders.cust_id ⊂ customer.cust_id?

a.
b.
c.
d.

• There exists an order without a customer.

• Every customer has placed an order.

• There exists a customer that has not placed an order.

• Every order has a customer.

1. In the ONLINE RETAILER example, what does it mean when item_supplier.supp_id = supplier.supp_id?

• There exists a supplier that supplies an item.

• Every item has a supplier.

• There exists an item that has a supplier.

• Every supplier supplies at least one item.