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

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.

Aprimary keyuniquely identifies each row in a table. When a primary key consists ofonly one field, it is called aSimple Primary Key.

Types of Primary Keys:

Simple Primary Key (Correct Answer):

Contains onlyone column.

Example:

sql

CREATE TABLE Students (

StudentID INT PRIMARY KEY,

Name VARCHAR(50)

);

Composite Primary Key:

Usesmultiple columnsto ensure uniqueness.

Example:

sql

CREATE TABLE Orders (

OrderID INT,

ProductID INT,

PRIMARY KEY (OrderID, ProductID)

);

Surrogate Primary Key:

A system-generatedunique identifier(e.g., UUID or AUTO_INCREMENT).

Why Other Options Are Incorrect:

Option B (Duplicate) (Incorrect):A primary keymust be unique, so itcannot be duplicate.

Option C (Numeric) (Incorrect):While primary keyscan be numeric, they can also be alphanumeric (VARCHAR).

Option D (Composite) (Incorrect):Acompositekey consists ofmultiple fields, whereas a simple key isa single field.

Thus, the correct answer isSimple, since aone-field primary keyis a simple primary key.

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.

AFull Join (FULL OUTER JOIN)selectsall records from both tables, filling in NULL values where there is no match. This ensures that no data is lost from either table.

Example Usage:

sql

SELECT Employees.Name, Departments.DepartmentName

FROM Employees

FULL OUTER JOIN Departments ON Employees.DeptID = Departments.ID;

This query retrievesall employees and all departments, even if an employeehas no assigned departmentor a departmenthas no employees.

Types of Joins:

FULL OUTER JOIN (Correct Answer)→ Includesall rows from both tables, filling missing values with NULL.

LEFT JOIN (Incorrect)→ Includesall rows from the left tableandmatching rows from the right table.

RIGHT JOIN (Incorrect)→ Includesall rows from the right tableandmatching rows from the left table.

CROSS JOIN (Incorrect)→ Produces aCartesian product(each row from one table is combined with every row from another table).

Thus, the correct answer isFULL JOIN, whichensures that all rows from both tables appear in the result.

In SQL, aprimary key is explicitly defined using the PRIMARY KEY keywordwhen creating a table.

Example Usage:

sql

CREATE TABLE Products (

ProductID INT PRIMARY KEY,

Name VARCHAR(100),

Price DECIMAL(10,2)

);

Here,PRIMARY KEY is the SQL keyword that designates ProductID as the primary key.

Why Other Options Are Incorrect:

Option A (Formula in SQL) (Incorrect):SQLdoes not use formulas to define primary keys.

Option C (Bold typeface) (Incorrect):SQL syntax does not rely on text formatting.

Option D (Diamond symbol) (Incorrect):ER diagramsmight use symbols, but SQLdoes not use diamonds to indicate keys.

Thus, the correct answer isSQL keyword, as primary keys are explicitly defined using PRIMARY KEY.

Thelogical design phasein database development focuses onstructuring data efficientlyto eliminate redundancy and ensure integrity. Thefinal step in logical designis toapply normalization (normal forms)to optimize the database schema.

Steps in Logical Database Design:

Discover entities→ Identify real-world objects (e.g., Customers, Orders).

Determine cardinality→ Define relationships between entities (one-to-one, one-to-many).

Analyze data requirements→ Determine the attributes each entity needs.

Apply normal forms→ Eliminate redundancy and improve data consistency.

Example Usage:

After identifying entities likeStudentsandCourses, applying3rd Normal Form (3NF)ensures that data isorganized without redundancy.

Why Other Options Are Incorrect:

Option A (Analyze data requirements) (Incorrect):Doneearlierto define attributes.

Option C (Determine cardinality) (Incorrect):Donebeforenormalization to establish relationships.

Option D (Discover entities) (Incorrect):Done at thebeginningof database design.

Thus, the correct answer isApply a normal form, as normalization is thelast step in logicaldesign.

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.

Toadd a primary key constraint after table creation, we use theALTER TABLEstatement.

Example Usage:

sql

ALTER TABLE Employees

ADD CONSTRAINT PK_Employees PRIMARY KEY (EmpID);

Thisaddsa primary key to the EmpID columnafter the table was created.

Why Other Options Are Incorrect:

Option B (CREATE TABLE) (Incorrect):Used for defining constraintsduringtable creation, not after.

Option C (UPDATE) (Incorrect):Modifiesrow values, not constraints.

Option D (INSERT INTO) (Incorrect):Used toadd datato a table, not modify constraints.

Thus, the correct answer isALTER TABLE, as itmodifies table structure to add a primary key constraint.

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.

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.

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.

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.

Aggregate functionsperform calculationson a set of values and return asingle result.MAX()is one such function, returning thelargest value in a column.

Common Aggregate Functions:

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Example Usage:

sql

SELECT MAX(Salary) FROM Employees;

Retrieves thehighest salaryin the Employees table.

Why Other Options Are Incorrect:

Option B (TRIM) (Incorrect):Removes spaces from strings butis not an aggregate function.

Option C (ABS) (Incorrect):Returns theabsolute value of a numberbut doesnot aggregate multiple rows.

Option D (DESC) (Incorrect):Used in ORDER BY forsorting in descending order,not for aggregation.

Thus, the correct answer isMAX(), as it is atrue aggregate function.

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.

TheBETWEENkeyword in SQL is used tofilter values within a specified range. It is particularly useful for numeric and date-based queries.

Syntax of BETWEEN:

sql

SELECT * FROM Employees WHERE Salary BETWEEN 50000 AND 100000;

Retrievesall employees whose salary is between $50,000 and $100,000 (inclusive).

Why Other Options Are Incorrect:

Option A (LIKE) (Incorrect):Used forpattern matchingwith wildcards (%, _). Example:

sql

SELECT * FROM Customers WHERE Name LIKE 'A%';

Option B (IN) (Incorrect):Used tomatch a value in a specified set, butnot a range. Example:

sql

SELECT * FROM Employees WHERE Department IN ('HR', 'Finance', 'IT');

Option C (OR) (Incorrect):Used forlogical conditions, but doesnot check a range. Example:

sql

SELECT * FROM Products WHERE Price < 10 OR Price > 50;

Thus, the correct choice is BETWEEN for filtering values within arange.