Question 1

The values of a candidate key of a relation ____.

Accepted Answer

The values of a candidate key must be unique. If they are not unique, they cannot serve as a candidate key. A candidate key is a minimal set of attributes that can uniquely identify each tuple in a relation. It can consist of a single attribute or multiple attributes.

Question 2

A candidate key of a relation that is not chosen to be the primary key ____.

Accepted Answer

A candidate key of a relation that is not chosen to be the primary key is called an alternate key.

Question 3

In a relation ____.

Accepted Answer

None of the given options fully define a relation. A relation is simply a set of ordered pairs, and the rows and columns can be arranged in any order or contain any number of duplicates. A cell in a relation can only have one value since each ordered pair has a unique combination of values for each attribute.

Question 4

The attribute(s) that make up a foreign key in a relation of a database ____.

Accepted Answer

A foreign key in a relation of a database must refer to a primary key in another relation, hence it must appear in another relation of the database. Option A is incorrect because the same attribute(s) may appear in another relation as long as they are not a primary key or part of one. Option B is incorrect because a foreign key has to refer to a primary key in another relation. Option D is incorrect because the values of a foreign key do not have to be unique in the relation in which it is a foreign key. Option E is incorrect because the foreign key does not have to be part of the primary key in the relation in which it is a foreign key, although it may be.

Question 5

An attribute or combination of attributes that is a foreign key in one relation of a database must be ____ another relation in the database.

Accepted Answer

A foreign key in one relation of a database must be the primary key of another relation in the database in order to establish a proper relationship between the two tables. This ensures referential integrity and helps maintain data consistency.

Question 6

The primary key of the relation added to accomplish the many-to-many relationship ____.

Accepted Answer

The primary key of the relation added in a many-to-many relationship should be the combination of the primary keys of the two relations involved in the relationship, plus any additional attributes necessary for the relationship. This new primary key then serves as the link between the two original relations.

Question 7

All of the following are true about storing a one-to-one binary relationship in a relational database, except _____.

Accepted Answer

The answer of All of the following are true about...

Question 8

The values of the primary key of a relation ____.

Accepted Answer

The primary key of a relation must be unique, as it is used to identify each tuple (row) in the relation. A primary key can consist of a single attribute or a combination of attributes. Therefore, option A and D are incorrect. Option B is partially correct, as a primary key may consist of non-unique attributes, but the combination of attributes must be unique. Option E is incorrect as well, as one of the given choices must be correct.

Question 9

A foreign key ____.

Accepted Answer

A foreign key must have the same domain of values as the primary key from which it is derived to ensure referential integrity between the two keys. This means the data type and constraints (like character length) should match, allowing the foreign key to correctly reference the primary key.

Question 10

The relational data model was first described in a paper by Dr. E. F. Codd in ____.

Accepted Answer

Dr. E. F. Codd first described the relational data model in a paper titled "A Relational Model of Data for Large Shared Data Banks," which was published in 1970.

Question 11

In relational database, the basic data structure that appears to be similar to a file is called a ____.

Accepted Answer

A relation in a relational database can be seen as a similar structure to a file in a traditional file-based system. It consists of rows and columns (also known as tuples and attributes) that organize and store data. However, unlike a file-based system, a relational database allows for more efficient data retrieval, querying, and management. The other options (attributes, records, columns, and rows) are components or elements of a relation, rather than the relation itself.

Question 12

An attribute(s) that acts as a foreign key in a relation ____.

Accepted Answer

An attribute that acts as a foreign key in a relation may also be part of the primary key of that relation, but it is not required to be the entire primary key. It can also be part of the primary key of another relation in the database. Therefore, option C is the correct answer.

Question 13

Storing a binary many-to-many relationship in a relational database ____.

Accepted Answer

Storing a binary many-to-many relationship in a relational database requires the addition of one additional relation, known as the join table or bridge table. This table contains foreign keys referencing the primary keys of the two entities being related in the many-to-many relationship.

Question 14

Doctors and patients are in a binary one-to-many relationship as:
 Doctor    Patient  To accomplish this in a relational database _____.

Accepted Answer

The answer of Doctors and patients are in a binary...

Question 15

An attribute(s) that functions as the primary key of relation A and as a foreign key in relation B of a relational database ____.

Accepted Answer

A primary key in relation A ensures uniqueness in A, but as a foreign key in relation B, it does not need to be unique, allowing for multiple records in B to relate to a single record in A.

Question 16

Which of the following relational algebra commands or combination of commands is capable of retrieving one or more rows of a relation?

Accepted Answer

The answer of Which of the following relational algebra commands...

Question 17

Relational database management first became commercially viable in ____.

Accepted Answer

The answer of Relational database management first became commercially viable...

Question 18

Which of the following relational algebra commands or combination of commands is capable of retrieving one or more columns of a relation?

Accepted Answer

The Project command is used to retrieve one or more columns from a relation. Select is used to retrieve specific rows based on a specified condition, Join is used to combine two relations based on a common attribute, and Select and Project can be combined to retrieve specific rows and columns from a relation. However, Select, Project, and Join together are not necessary to retrieve columns from a relation.

Question 19

Consider relations X and Y, each representing one of two entities in a many-to-many binary relationship. Relation Z is the additional relation created to store the many-to-many relationship. Intersection data ____.

Accepted Answer

Intersection data for a many-to-many relationship is stored in a separate relation, which is relation Z in this context. This relation typically contains foreign keys that reference the primary keys of the two entities involved in the relationship.

Question 20

All of the following events and factors in the early 1980s led to the introduction of relational database management, except ____.

Accepted Answer

Improvements in mainframe computer performance did not directly lead to the introduction of relational database management. The other options are all directly related to the need for a simpler and more efficient database management approach for personal computers.

Quiz 5: The Relational Database Model: Introduction