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

TheCASCADEconstraint ensures thatupdates or deletions in the primary key table automatically reflect in the foreign key 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) ON UPDATE CASCADE ON DELETE CASCADE

);

If DeptIDchangesin Departments, itautomatically updatesin Employees.

If a DeptID isdeleted, all employees in that departmentare also deleted.

Why Other Options Are Incorrect:

Option A (SET DEFAULT) (Incorrect):Sets foreign key values to adefaultvalue, rather than propagating changes.

Option B (SET NULL) (Incorrect):When the referenced key is deleted, dependent records areset to NULLinstead of being updated/deleted.

Option C (RESTRICT) (Incorrect):Prevents deletion of a referenced row if dependent foreign key rows exist.

Thus, the correct answer isCASCADE, as itpropagates primary key changes to dependent foreign keys.

When performing aJOIN operationin MySQL, the ON clause specifies thejoining condition, defining which columns from both tables should be matched.

Example:

sql

SELECT Employees.Name, Departments.DepartmentName

FROM Employees

JOIN Departments ON Employees.DepartmentID = Departments.ID;

Option A (Incorrect):AS is used foraliasing tables and columns, not for specifying join conditions.

Option B (Incorrect):JOIN defines the type of join (INNER JOIN, LEFT JOIN, etc.), butdoes not specify the columns.

Option C (Correct):The ON clause is used tospecify the join conditionbetween two tables.

Option D (Incorrect):AND is used in filtering conditions, not for joining tables.

Adata typedefines the kind of data a column can store in a database. It ensures data consistency and efficient storage.

Option A (Correct):A data type is anamed set of values, such asINTEGER, VARCHAR, DATE, etc.

Option B (Incorrect):A tuple refers to arowin a relational database, not a data type.

Option C (Incorrect):Data typesdefinecolumn values, but they do not correspond directly to columns.

Option D (Incorrect):Data types do not have avaryingset of rows; they define attributes for columns.

Areflexive relationship(also called aunary relationship) occurs when anentity is related to itself.

Example Usage:

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CREATE TABLE Employees (

EmpID INT PRIMARY KEY,

Name VARCHAR(50),

ManagerID INT,

FOREIGN KEY (ManagerID) REFERENCES Employees(EmpID)

);

ManagerIDrefers to another employeewithin the same table.

Why Other Options Are Incorrect:

Option A (Repository) (Incorrect):A data storage structure, not a relationship type.

Option B (Relationship instance) (Incorrect):Describesa specific connection between entities, not a reflexive relationship.

Option D (Attribute) (Incorrect):Attributes storecharacteristics, butdo not define relationships.

Thus, the correct answer isReflexive relationship, as it relates an entity to itself.

Non-relational databases(also calledNoSQL databases) are designed for handlingbig dataandunstructured dataefficiently. They are optimized forhorizontal scaling, making them ideal forlarge-scale distributed systems.

Option A (Correct):Non-relational databases areoptimized for big data, handling massive volumes of data across distributed architectures.

Option B (Incorrect):NoSQL databases donotuse SQL as their primary query language. They often use JSON-based queries (e.g., MongoDB).

Option C (Incorrect):Transaction-heavy applications requireACID compliance, which relational databases (SQL) handle better than NoSQL databases.

Option D (Incorrect):NoSQL databases usedocument, key-value, graph, or column-family storage models, nottables, columns, and rowslike relational databases.

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.

Information independencerefers to theseparation between data storage and data access. It allows a database’slogical structureto be modifiedwithout affecting existing applications.

Types of Information Independence:

Logical Data Independence→ Ability to change theconceptual schema(e.g., renaming columns, adding new attributes)without modifying applications.

Physical Data Independence→ Ability to change thephysical storage structure(e.g., indexing, partitioning)without affecting queries.

Example of Logical Data Independence:

Anew columnis added to the Customers table, but existing queriesstill work without modification.

Example of Physical Data Independence:

Data is moved to SSD storagefor performance improvement, but queriesrun the same way.

Why Other Options Are Incorrect:

Option A (Incorrect):Changing thedatabase type(e.g., MySQL to PostgreSQL) isnotinformation independence.

Option B (Incorrect):Making changes toqueriesis unrelated to database independence.

Option C (Incorrect):Interchanging databases is related todata portability, notinformation independence.

Thus, the correct answer isD - An ability to change the organization of data, asinformation independenceensuresmodifications do not disrupt database operations.

Databases need to supportApplication Programming Interfaces (APIs)to enable seamless integration withgeneral-purpose programming languageslike Python, Java, and C#. APIs likeODBC (Open Database Connectivity) and JDBC (Java Database Connectivity)allow applications to interact with databases without requiring complex SQL commands.

Option A (Incorrect):Thestorage manageris responsible for managing low-levelfile system operations, but it does not simplify SQL integration with programming languages.

Option B (Incorrect):The ability toreverse results(e.g., using ORDER BY DESC) is a SQL feature but is unrelated to integration with programming languages.

Option C (Incorrect):Thequery processoroptimizes and executes SQL queries but does not provide an interface for application development.

Option D (Correct):APIsallow databases to be accessed easily from different programming environments, simplifying integration.

Attributesin a databaserepresent the properties (names, values, or characteristics) of an entity.

Example Usage:

In aStudentstable, attributes might include:

StudentID (Primary Key), Name, Age, Major

Here,Name is an attributedescribing the entityStudent.

Why Other Options Are Incorrect:

Option A (Synonyms) (Incorrect):Synonyms in SQL allow different names for the same object but arenot attributes.

Option C (Repositories) (Incorrect):A repository stores data butdoes not define attributes.

Option D (Relationships) (Incorrect):Relationships defineconnections between entities, not their attributes.

Thus, the correct answer isNames, asattributes define entity properties.