DATABASE DESIGN, ENTITY-RELATIONSHIP
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Question 1: In a one-one relationship, the _____ key is often placed in the table with fewer
rows. This minimizes the number of _____ values.
A) primary, NULL
B) foreign, unique
C) primary, unique
D) foreign, NULL
- answers 100%✔✔✔ 📌D) foreign, NULL
Rationale: In a one-to-one relationship, placing the foreign key in the table with fewer rows
minimizes NULL values because there are fewer rows that would potentially need NULL entries
for the foreign key column. This is a database design optimization technique that reduces
storage waste and maintains data integrity. The foreign key references the primary key of the
related table, and by placing it in the table with fewer rows, we ensure fewer NULL values
appear in that column since not all rows in the larger table would have corresponding matches.
Question 2: Which goes in the table on the "many" side of a one-many relationship?
,A) Optional attribute
B) Foreign key
C) Artificial key
D) Primary key
- answers 100%✔✔✔ 📌B) Foreign key
Rationale: In a one-to-many relationship, the foreign key is placed in the table on the "many"
side because each record on the many side needs to reference the single related record on the
one side. For example, if one Department has many Employees, the DepartmentID foreign key
goes in the Employee table (the many side). This design ensures referential integrity and allows
proper relationship implementation without creating redundant data.
Question 3: Each course must be offered by at least one department. In the Department-Offers-
Course relationship, Department is a(n) _____ entity.
A) plural
B) optional
C) singular
D) required
- answers 100%✔✔✔ 📌D) required
Rationale: Since each course must be offered by at least one department, the Department
entity is required in this relationship. The word "must" indicates a mandatory relationship
where every Course instance requires a corresponding Department instance. A required entity
means that participation in the relationship is mandatory, not optional, for all instances of that
entity type.
Question 4: When implementing relationships, each many-one relationship becomes a _____
key.
A) foreign
B) primary
C) NULL
D) artificial
- answers 100%✔✔✔ 📌A) foreign
,Rationale: When implementing a many-to-one relationship in a relational database, the primary
key from the "one" side becomes a foreign key in the "many" side table. This allows multiple
records in the many-side table to reference a single record in the one-side table. The foreign key
constraint ensures referential integrity by requiring that values in the foreign key column match
existing values in the referenced primary key column.
Question 5: During database design, an ER _____ and _____ are usually developed in parallel.
A) entity, relationship
B) repository, dictionary
C) diagram, glossary
D) analysis, relationship
- answers 100%✔✔✔ 📌C) diagram, glossary
Rationale: During database design, the Entity-Relationship diagram (visual representation) and
the glossary (textual definitions of terms, attributes, and business rules) are developed
simultaneously. The diagram provides a graphical overview of entities and their relationships,
while the glossary provides detailed documentation of meanings, data types, and constraints.
Together, they form complementary documentation that ensures comprehensive understanding
of the database design.
Question 6: A model has Shipment, Product, and Shipper entities. The Shipment entity has no
unique attributes. Each shipment is identified by ProductNumber, ShipperCode, and
ShipmentDate. Shipment is a(n) _____ entity.
A) strong
B) identifying
C) weak
D) subtype
- answers 100%✔✔✔ 📌C) weak
Rationale: Shipment is a weak entity because it has no unique attributes of its own and must be
identified through its relationship with other entities (Product and Shipper). The combination of
ProductNumber, ShipperCode, and ShipmentDate from related entities serves as the composite
identifier. Weak entities depend on identifying relationships with strong entities for their
existence and unique identification.
, Question 7: Each value of a _____ attribute describes at most one entity instance.
A) unique
B) singular
C) required
D) plural
- answers 100%✔✔✔ 📌A) unique
Rationale: A unique attribute has values that describe at most one entity instance, meaning no
two entity instances can share the same value for that attribute. This is the defining
characteristic of unique attributes, which can serve as candidate keys or primary keys. For
example, a Social Security Number is unique because each value identifies exactly one person.
Question 8: What is an optional attribute?
A) Each attribute value describes at least one entity instance.
B) Each entity instance has at least one attribute value.
C) Each entity instance can have zero attribute values.
D) Each attribute value can describe zero entity instances.
- answers 100%✔✔✔ 📌C) Each entity instance can have zero attribute values.
Rationale: An optional attribute is one where entity instances may or may not have a value. This
means an entity instance can have zero attribute values for that particular attribute. Optional
attributes are common in databases where certain information may not be available for all
records, such as a middle name or secondary phone number. When implemented, optional
attributes allow NULL values.
Question 9: Optional attributes and relationships become columns that allow for _____ values.
A) artificial
B) subtype
C) composite
D) NULL
- answers 100%✔✔✔ 📌D) NULL