Pass the WGU Courses and Certificates Data-Management-Foundations Questions and answers with ValidTests

In database indexing, abranchrefers to thepath from the top-level block (root node) to a bottom-level block (leaf node)in aB-Tree or B+ Tree index structure.

Example Usage in Indexing:

AB-Tree indexorganizes data hierarchically, withbranches leading to different parts of the tree.

When searching for a record, thequery follows a branchfrom theroot node down to the correct leaf node.

Why Other Options Are Incorrect:

Option A (Fan-out) (Incorrect):Refers tohow many children a node has, not the path.

Option B (Crow’s foot) (Incorrect):Anotation used in ER diagrams, not indexing.

Option D (Sparse index) (Incorrect):A type of indexstoring only some entries, not the path itself.

Thus, the correct answer isBranch, as it defines thepath from top to bottom in a database index.

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.

Anindex scanis a database operation thatquickly locates table blocksusing anindexrather than scanning the entire table. It significantly improves query performance.

Example Usage:

sql

SELECT * FROM Employees WHERE EmployeeID = 105;

If EmployeeID isindexed, the database uses anindex scantoquickly find the record.

Why Other Options Are Incorrect:

Option A (Binary search) (Incorrect):A searching algorithm, but not a database operation.

Option B (Table scan) (Incorrect):Scans theentire table, which isslowerthan an index scan.

Option C (Fan-out) (Incorrect):Refers tobranching in B-Treesbut doesnot locate table blocks directly.

Thus, the correct answer isIndex scan, as it efficiently locates table blocks.

Atangible entityis a real-world object that can bemeasured and storedin a database.

Example Usage:

In an inventory system,tangible entitiesinclude:

Products, Orders, Customers

Why Other Options Are Incorrect:

Option A (Logical entity) (Incorrect):Exists logically butmay not have a physical presence(e.g.,views, categories).

Option C (Virtual entity) (Incorrect):Existsonly in queries or reports, not stored as real data.

Option D (Conceptual entity) (Incorrect):Abstract idea used indesign modeling, not astored entity.

Thus, the correct answer isTangible entity, as it representsmeasurable, real-world objects.

Anintangible entityis an entity that does not have a physical presence but still holds meaning in a database. These entities representconcepts, relationships, or abstract datathat exist in a logical sense.

Example Usage in Databases:

Customer Loyalty Status (Gold, Silver, Bronze)

Theloyalty levelis anintangible entitysince it is derived from other data (purchase history).

Online User Sessions

Asession IDexistslogically in the systembut does not have a tangible presence like a product or employee.

Why Other Options Are Incorrect:

Option A (Concrete entity) (Incorrect):No such formal term in database design.

Option B (Tangible entity) (Incorrect):Represents somethingphysical, like anemployeeorproduct.

Option D (Physical entity) (Incorrect):Refers todata stored on disk, like database tables or indexes.

Thus, the correct answer isIntangible entity, as it only exists in a logical sense within the database.

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.

TheALTER TABLEstatement is used to modify an existing database table structure. One common clause isCHANGE, which allows renaming a column and modifying its data type.

Example:

sql

ALTER TABLE Employees CHANGE COLUMN OldName NewName VARCHAR(50);

Option A (Incorrect):DELETE is used to removerows, not alter table structure.

Option B (Correct):CHANGE is avalid clausefor renaming and modifying columns in MySQL and some other databases.

Option C (Incorrect):STOP is not a valid SQL keyword for altering tables.

Option D (Incorrect):AGGREGATE refers to functions like SUM() and AVG(), not table alterations.

TheCHECKconstraint is used in SQL toenforce ruleson a column's values. It ensures that data inserted into a table meets specified conditions, such as range restrictions or logical rules.

Example Usage:

sql

CREATE TABLE Employees (

ID INT PRIMARY KEY,

Name VARCHAR(50),

Salary INT CHECK (Salary BETWEEN 30000 AND 150000)

);

This constraint ensures thatsalary values fall between 30,000 and 150,000.

If an INSERT or UPDATE statement tries to set Salary = 20000, itfailsbecause it does notmeet the CHECK condition.

Why Other Options Are Incorrect:

Option B (FROM) (Incorrect):Used in SELECT statements, not for constraints.

Option C (WHERE) (Incorrect):Filters rows in queries butdoes not enforce constraints.

Option D (SET) (Incorrect):Used for updating records (UPDATE table_name SET column = value) butnot for defining constraints.

Thus,CHECK is the correct answer, as it ensures that column values remain within an expected range.

Avalid SELECT statementin SQL follows this basic syntax:

sql

SELECT column1, column2

FROM table_name

WHERE condition;

The correct optionDfollows this syntaxcorrectly.

Why Other Options Are Incorrect:

Option A (Incorrect):SQL does not usedouble quotes(") around column/table names unless explicitly required in some databases.

Option B (Incorrect):The WHERE clausemust appear after the FROM clause.

Option C (Incorrect):ALL isnota valid keyword in standard SQL queries.

Thus,Option Dfollows the correct SQL syntax.