WGU Updated Data-Management-Foundations Exam Questions and Answers by loki

Asimple primary keyconsists ofonly one columnthat uniquely identifies each row in a table.

Example Usage:

sql

CREATE TABLE Students (

StudentID INT PRIMARY KEY,

Name VARCHAR(50)

);

StudentIDis asimple primary keybecause it consists of only one field.

Why Other Options Are Incorrect:

Option B (Partition) (Incorrect):Refers topartitioned tables, which divide data for performance reasons butare not related to primary keys.

Option C (Stable) (Incorrect):This is not a recognized term in database keys.

Option D (Meaningless) (Incorrect):Primary keys are oftenmeaningless (e.g., auto-incremented IDs), but this isnot a term used to describe their structure.

Thus, the correct answer isSimple, as asingle-field primary keyis referred to as asimple primary key.

Aforeign keyis a column (or a set of columns) that establishes arelationship between two tablesby referencing theprimary key of another table.

Example Usage:

sql

CREATE TABLE Departments (

DeptID INT PRIMARY KEY,

DeptName VARCHAR(50)

);

CREATE TABLE Employees (

EmpID INT PRIMARY KEY,

Name VARCHAR(50),

DeptID INT,

FOREIGN KEY (DeptID) REFERENCES Departments(DeptID)

);

DeptID in Employees is a foreign key, referencing DeptID in Departments.

Ensuresreferential integrity→ DeptID in Employeesmust existin Departments.

Why Other Options Are Incorrect:

Option A (Super key) (Incorrect):Asuper keyis any set of columns that uniquely identifies a row, but itdoes not reference another table.

Option B (Simple key) (Incorrect):Asimple keyis asingle-column primary key, not a reference to another table.

Option C (Composite key) (Incorrect):Acomposite keyconsists ofmultiple columnsbut does not necessarily reference another table.

Thus, the correct answer isForeign key, as it establishes aconnection between two tables.

ATransaction ManagerensuresACID (Atomicity, Consistency, Isolation, Durability)properties in database transactions. It manages concurrent transactions, ensuring no conflicts occur and logs modifications to support recovery mechanisms.

Option A (Incorrect):Query optimization is managed by thequery processor, not the transaction manager.

Option B (Incorrect):The transaction manager is a component of the database architecture but is not composed of the entire system (query processor, storage manager, etc.).

Option C (Correct):The transaction manager logs transactions like INSERT, UPDATE, and DELETE, ensuring consistency and recoverability.

Option D (Incorrect):Thestorage manageris responsible for translating queries into filesystem commands.

The given diagram represents a unary relationship (also called a recursive relationship), which occurs when an entity is related to itself. In this case, salespersons back each other up, meaning a salesperson is associated with another salesperson from the same entity.

Key Observations from the Diagram:

Single Entity (Salesperson)

The table contains only one entity type, Salesperson, which has attributes such as Salesperson Number, Name, Commission, Percentage, and Year of Hire.

Self-Referencing Relationship (Backs-up and Backed-up by)

The diagram shows that a salesperson can back up another salesperson.

This means that the relationship exists within the same entity rather than between two different entities.

Cardinality (One-to-One Relationship in a Unary Form)

The notation ( |—| ) in the ER diagram indicates a one-to-one recursive relationship.

One salesperson can back up only one other salesperson, and each salesperson is backed up by only one.