WGU Data-Management-Foundations - WGU Data Management – Foundations Exam

Aunary relationship(also known as arecursive relationship) occurs when an entityrelates to itself.

Example Usage:

Employees and Managers:

sql

CREATE TABLE Employees (

EmpID INT PRIMARY KEY,

Name VARCHAR(50),

ManagerID INT,

FOREIGN KEY (ManagerID) REFERENCES Employees(EmpID)

);

Here, ManagerIDreferences another Employee→ aunary (self-referential) relationship.

Why Other Options Are Incorrect:

Option A (Modality) (Incorrect):Describesoptional vs. mandatoryrelationships, not self-referencing.

Option C (Cardinality) (Incorrect):Defines how many instances relate,not the type of relationship.

Option D (Binary) (Incorrect):Binary relationships involvetwo different entities, not self-referencing.

Thus, the correct answer isUnary, as it describesrelationships within the same entity type.

Aquery processoris responsible forquery optimization and executionin a database management system (DBMS). It analyzes SQL statements, optimizes execution plans, and ensures efficient retrieval of data.

Option A (Correct):Thequery processoroptimizes queries by analyzing metadata from thesystem catalogto determine the best execution strategy.

Option B (Incorrect):Logging transactionsbefore applying changes is the responsibility of thetransaction manager.

Option C (Incorrect):Translating instructions intofile system commandsis handled by thestorage manager, not the query processor.

Option D (Incorrect):While the query processor helps retrieve results, thedatabaseengineandAPI layerare responsible for returning results to applications.

TheONkeyword specifies the field used by anindexwhen creating it in SQL.

Example Usage:

sql

CREATE INDEX idx_employee_name

ON Employees(Name);

Here, an indexidx_employee_nameis createdon the Name column.

Thisimproves query performancewhen filtering by Name.

Why Other Options Are Incorrect:

Option B (IN) (Incorrect):Used in queries to match values in a set, not for indexing.

Option C (UNIQUE) (Incorrect):Ensures a column has unique values but doesnot define an index field.

Option D (CHECK) (Incorrect):Used forvalidating column values, not for indexing.

Thus, the correct answer isON, as it defines thecolumn on which an index is created.

TheABS()function in SQL returns theabsolute valueof a given number, effectively measuring itsdistance from zero.

Example Usage:

sql

SELECT ABS(-50), ABS(50);

Result:

50 | 50

This function ensures that numbers arealways positive, regardless of their original sign.

Why Other Options Are Incorrect:

Option A (CONCAT) (Incorrect):Used tocombine strings(not numbers).

Option B (LOWER) (Incorrect):Converts text tolowercase, not numerical operations.

Option C (FROM) (Incorrect):Part of SELECT FROM queries,not a function.

Thus, the correct choice isABS(), which computes the absolute value of a number.

MongoDB is aNoSQL (non-relational) databasethat isopen-sourceand supportsdocument-oriented storage. It allows for flexible schema design and is optimized for big data applications.

Option A (Correct):MongoDB is aNoSQL databasewith an open-sourceAGPLlicense, making it both free to use and non-relational.

Option B (Incorrect):SQL Serveris arelational database(RDBMS) developed by Microsoft and isnot open-source.

Option C (Incorrect):MySQLisopen-sourcebut is arelational database(RDBMS), not a NoSQL system.

Option D (Incorrect):Oracle Databaseisrelationalandproprietary(not open-source).

Thesecond step in implementing relationshipsis definingone-to-one (1:1) relationshipsbetween entities.

Example Usage:

Example of a 1:1 relationship:

sql

CREATE TABLE Employees (

EmpID INT PRIMARY KEY,

Name VARCHAR(50)

);

CREATE TABLE EmployeeDetails (

EmpID INT PRIMARY KEY,

Address VARCHAR(255),

FOREIGN KEY (EmpID) REFERENCES Employees(EmpID)

);

Here, eachemployee has exactly one detail record, creating a1:1 relationship.

Why Other Options Are Incorrect:

Option A (Implement weak entities) (Incorrect):Weak entities rely on aforeign keyand are implementedlater.

Option C (Implement subtype entities) (Incorrect):Subtypes arespecial casesandnot implemented in the second step.

Option D (Specify cascade) (Incorrect):Cascade rules (ON DELETE, ON UPDATE)are defined duringforeign key implementation, not in the second step.

Thus, the correct answer isImplement one-one relationships, as it is thenext logical stepafter defining entities.

Cardinalitydefines theminimum and maximum number of occurrencesof one entity in relation to another.

Example Usage in an ER Model:

One-to-Many (1:M): Acustomer can place multiple orders, but each order belongs to onlyonecustomer.

Customers (1) ——— (M) Orders

Cardinality notation:

(1,1) → One-to-One

(0,M) → Zero-to-Many

(1,M) → One-to-Many

Why Other Options Are Incorrect:

Option B (Physical design) (Incorrect):Focuses onstorage and indexing, not relationships.

Option C (Attribute minimum) (Incorrect):No such formal term in database modeling.

Option D (Partition) (Incorrect):Refers todividing tables, not relationship constraints.

Thus, the correct answer isCardinality, as it definesmin/max constraints on relationships.

Indatabase modeling, the relationship between asupertype and its subtypesis called anIsA relationship.

Example Usage:

AVehicle supertypemay haveCar and Truck subtypes.

Vehicle

├── Car

├── Truck

InER diagrams, this is represented as:

Vehicle (Supertype)

|

├── Car (Subtype)

├── Truck (Subtype)

SQL Table Implementation:

sql

CREATE TABLE Vehicle (

VehicleID INT PRIMARY KEY,

Make VARCHAR(50),

Model VARCHAR(50)

);

CREATE TABLE Car (

VehicleID INT PRIMARY KEY,

FOREIGN KEY (VehicleID) REFERENCES Vehicle(VehicleID),

EngineType VARCHAR(50)

);

CREATE TABLE Truck (

VehicleID INT PRIMARY KEY,

FOREIGN KEY (VehicleID) REFERENCES Vehicle(VehicleID),

CargoCapacity INT

);

This structurepreserves the IsA relationshipbetween Vehicle (supertype) and Car/Truck (subtypes).

Why Other Options Are Incorrect:

Option A (Strong entity) (Incorrect):Strong entitiesdo not rely on a supertype/subtype hierarchy.

Option C (Associative entity) (Incorrect):Used toresolve many-to-many relationships, not supertype/subtype relationships.

Option D (Weak entity) (Incorrect):Weak entitiesdepend on a strong entity, but supertype-subtype relations useinheritance(not dependency).

Thus, the correct answer isIsA relationship, as it describes theinheritance hierarchybetweensupertypes and subtypes.