Data-Management-Foundations WGU Data Management – Foundations Exam Questions and Answers

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.

In MySQL, theBIGINTdata type is a64-bit integerthat requires8 bytes (64 bits) of storage. It is used to store large numerical values beyond the range of INT (4 bytes).

Option A (Incorrect):1 byte corresponds toTINYINT, which can store values from -128 to 127.

Option B (Incorrect):3 bytes is not a standard integer storage size in MySQL.

Option C (Incorrect):4 bytes corresponds toINT, which has a range of -2,147,483,648 to 2,147,483,647.

Option D (Correct):BIGINT takes8 bytesand supports a massive range of numbers from -2^63 to 2^63 -1.

TheLTRIM()function in SQL removesleading spaces(spaces at the beginning of a string) while keeping spaces at the end.

Example Usage:

sql

SELECT LTRIM(' Hello World') AS TrimmedText;

Output:

bash

'Hello World'

Why Other Options Are Incorrect:

Option B (LEFT) (Incorrect):Used for extracting a portion of a string. Example:

sql

SELECT LEFT('Hello World', 5); -- Output: 'Hello'

Option C (TRIM) (Incorrect):Removesboth leading and trailing spaces, not just leading ones. Example:

sql

SELECT TRIM(' Hello World '); -- Output: 'Hello World'

Option D (REPLACE) (Incorrect):Replaces occurrences of one substring with another but doesnot specifically remove spaces.

Thus, the correct answer isLTRIM(), which removes onlyleading spaces.

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.

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.

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.

TheORDER BYclause in SQL is used tosort query resultsinascending (ASC) or descending (DESC) order.

Example Usage:

sql

SELECT Name, Salary FROM Employees ORDER BY Salary DESC;

This retrieves all employees, sorted bysalary in descending order.

Why Other Options Are Incorrect:

Option A (BETWEEN) (Incorrect):Used for filtering ranges butdoes not order results.

Option B (DISTINCT) (Incorrect):Removes duplicate rows butdoes not control order.

Option D (LIKE) (Incorrect):Used forpattern matching, not sorting.

Thus,ORDER BY is the correct choicefor defining the sequence of query results.

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.

TheMERGEstatement, also known asUPSERT, combinesINSERT, UPDATE, and DELETEoperations into asingle statementbased on a given condition. It is commonly used indata warehouses and large-scale databases.

Example Usage:

sql

MERGE INTO Employees AS Target

USING NewEmployees AS Source

ON Target.ID = Source.ID

WHEN MATCHED THEN

UPDATE SET Target.Salary = Source.Salary

WHEN NOT MATCHED THEN

INSERT (ID, Name, Salary) VALUES (Source.ID, Source.Name, Source.Salary);

If a match is found, the UPDATE clause modifies the existing record.

If no match is found, the INSERT clause adds a new record.

Why Other Options Are Incorrect:

Option A (INTO) (Incorrect):Used in INSERT INTO, butdoes not combine operations.

Option B (JOIN) (Incorrect):Used to combine rows from multiple tables, butnot for merging data.

Option D (DROP) (Incorrect):Deletes database objects liketables, views, and indexes, butdoes not merge data.

Thus, the correct answer isMERGE, as itcombines inserts, updates, and deletes into a single operation.

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.

This query performs ajoin operationwhere records from the Make table and Model table are combined based on the condition Make.ModelID = Model.ID. This conditiontests for equality, which is the definition of anEQUIJOIN.

Types of Joins in SQL:

EQUIJOIN (Correct Answer):

Uses an equality operator (=) to match rows between tables.

Equivalent to an INNER JOIN ON condition.

Example:

sql

SELECT *

FROM Employees

JOIN Departments ON Employees.DeptID = Departments.ID;

NON-EQUIJOIN (Incorrect):

Usescomparison operators other than =(e.g., <, >, BETWEEN).

Example:

sql

SELECT *

FROM Employees e

JOIN Salaries s ON e.Salary > s.MedianSalary;

SELF JOIN (Incorrect):

A table is joined withitselfusing table aliases.

Example:

sql

SELECT e1.Name, e2.Name AS Manager

FROM Employees e1

JOIN Employees e2 ON e1.ManagerID = e2.ID;

CROSS JOIN (Incorrect):

ProducesCartesian product(each row from Table A combines with every row from Table B).

Example:

sql

SELECT *

FROM Employees

CROSS JOIN Departments;

Thus, since our given query uses anequality condition (=) to join two tables, it is anEQUIJOIN.

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.

TheUNIONkeyword in SQL is used tocombine the resultsof two or more SELECT queries into asingle result setwhile removing duplicate rows.

Example:

sql

SELECT Name FROM Employees

UNION

SELECT Name FROM Managers;

Option A (Correct):UNION combines results from multiple queries into one set,removing duplicates.

Option B (Incorrect):MERGE is not a valid SQL keyword for combining result sets (it is used insome database systems for data merging).

Option C (Incorrect):INTEGRATE is not a SQL keyword.

Option D (Incorrect):CONSOLIDATE is not an SQL keyword.

ADatabase Administrator (DBA)is responsible for the management, security, and performance of a database system. This includes controlling access to data, ensuring database integrity, optimizing performance, managing backups, and protecting the system from unauthorized access.

Option A (Incorrect):A DBA is not just a consumer of data but is primarily responsible for the database’s management.

Option B (Correct):Security is one of the key responsibilities of a DBA, including enforcing user access controls and implementing encryption and authentication mechanisms.

Option C (Incorrect):While DBAs work with data structures, it is typically the role of adata architectordatabase designerto define data formats and schema structures.

Option D (Incorrect):Developing application programs that interact with the database is typically the role ofsoftware developersordatabase programmers, not DBAs.

The % operator in MySQL is known as themodulus operator. It returns theremainderof a division operation between two numbers.

Example:

sql

SELECT 10 % 3; -- Output: 1 (10 divided by 3 gives remainder 1)

Option A (Incorrect):Raising a number to a power is done using the POW() function or ^ in some SQL dialects.

Option B (Incorrect):The = operator is used forequality comparisons, not %.

Option C (Correct):Themodulus operator (%)finds the remainder when one number is divided by another.

Option D (Incorrect):Subtraction is performed using the - operator.