WGU D427 Data Management Applications ACTUAL EXAM QUESTIONS AND ANSWERS 2026/2027 | OA & Pre-Assessment | Complete Test Bank | Verified Answers | Pass Guaranteed - A+ Graded

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WGU D427 Data Management Applications ACTUAL
EXAM QUESTIONS AND ANSWERS 2026/2027 | OA
& Pre-Assessment | Complete Test Bank | Verified
Answers | Pass Guaranteed - A+ Graded
WGU D427 Data Management Applications

OA and Pre-Assessment Simulation

SCHEMA REFERENCE:

Use the following tables for all questions:

Students (StudentID, FirstName, LastName, Email, EnrollmentDate, Major)

Courses (CourseID, CourseCode, CourseName, Credits, Department)

Instructors (InstructorID, FirstName, LastName, Email, HireDate)

Enrollments (EnrollmentID, StudentID, CourseID, InstructorID, Semester, Grade,
EnrollmentDate)

Competency 1: SQL Basics and Data Definition Language (DDL)

Questions 1-15

Question 1

Which SQL statement is used to modify the structure of an existing table by adding a new
column?

A. MODIFY TABLE

B. ALTER TABLE **[CORRECT]**

C. UPDATE TABLE

D. CHANGE TABLE

Correct Answer: B

Rationale: ALTER TABLE is the correct DDL statement for modifying existing table structures,
including adding, modifying, or dropping columns. Distractor A (MODIFY TABLE) is not valid
SQL syntax. Distractor C (UPDATE TABLE) is incorrect because UPDATE is a DML command
for modifying data, not structure. Distractor D (CHANGE TABLE) is not standard SQL syntax.

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Question 2

What is the maximum number of PRIMARY KEY constraints that can be defined on a single
table?

A. Unlimited

B. 2

C. 1 **[CORRECT]**

D. 3

Correct Answer: C

Rationale: A table can have only one PRIMARY KEY constraint, which uniquely identifies each
row and cannot contain NULL values. While a table can have multiple UNIQUE constraints,
only one PRIMARY KEY is allowed. Distractors A, B, and D are incorrect because SQL
standards limit PRIMARY KEY to one per table.

Question 3

Which data type would be most appropriate to store a student's GPA with values like 3.85?

A. INT

B. VARCHAR(10)

C. DECIMAL(3,2) **[CORRECT]**

D. DATE

Correct Answer: C

Rationale: DECIMAL(3,2) is optimal for GPA values because it stores 3 total digits with 2
decimal places (e.g., 3.85, 4.00). Distractor A (INT) cannot store decimal values. Distractor B
(VARCHAR) stores text, making mathematical operations difficult. Distractor D (DATE) is for
temporal data only.

Question 4

What happens when you execute DROP TABLE Students;?

A. Only the data is deleted, table structure remains

B. The table structure and all data are permanently removed **[CORRECT]**

C. The table is renamed to "Students_old"

D. Only the constraints are removed

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Correct Answer: B

Rationale: DROP TABLE is a DDL command that permanently removes both the table structure
and all associated data, indexes, triggers, and constraints. Distractor A describes TRUNCATE
TABLE. Distractor C describes no standard SQL operation. Distractor D is incorrect as
constraints are removed with the table.

Question 5

Which SQL command creates a table with a composite primary key consisting of StudentID and
CourseID?

A. CREATE TABLE Enrollment (StudentID INT PRIMARY KEY, CourseID INT PRIMARY
KEY);

B. CREATE TABLE Enrollment (StudentID INT, CourseID INT, PRIMARY KEY (StudentID,
CourseID)); **[CORRECT]**

C. CREATE TABLE Enrollment (StudentID INT PRIMARY KEY, CourseID INT FOREIGN
KEY);

D. CREATE TABLE Enrollment (StudentID INT UNIQUE, CourseID INT UNIQUE);

Correct Answer: B

Rationale: A composite primary key is defined at the table level by listing multiple columns in
the PRIMARY KEY constraint. Distractor A attempts two PRIMARY KEY constraints, which is
invalid. Distractor C incorrectly uses FOREIGN KEY syntax. Distractor D creates two separate
unique constraints, not a composite key.

Question 6

What is the purpose of the UNIQUE constraint?

A. Ensures the column cannot contain NULL values

B. Ensures all values in the column are different **[CORRECT]**

C. Establishes a relationship between tables

D. Automatically increments the column value

Correct Answer: B

Rationale: UNIQUE ensures no duplicate values exist in the column (except multiple NULLs in
some DBMS). Distractor A describes NOT NULL. Distractor C describes FOREIGN KEY.
Distractor D describes AUTO_INCREMENT or IDENTITY.

Question 7

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Which statement correctly adds a CHECK constraint to ensure Credits in the Courses table is
always greater than 0?

A. ALTER TABLE Courses ADD CONSTRAINT chk_credits CHECK (Credits > 0);
**[CORRECT]**

B. ALTER TABLE Courses MODIFY Credits CHECK > 0;

C. UPDATE Courses SET CHECK (Credits > 0);

D. CREATE CHECK ON Courses (Credits > 0);

Correct Answer: A
Rationale: The correct syntax uses ALTER TABLE with ADD CONSTRAINT, naming the
constraint and specifying the CHECK condition. Distractor B uses incorrect MODIFY syntax.
Distractor C incorrectly places CHECK in an UPDATE statement. Distractor D uses invalid
CREATE CHECK syntax.

Question 8

What is the result of executing CREATE TABLE NewStudents AS SELECT * FROM Students;?

A. An error because AS SELECT is not valid syntax

B. A new table NewStudents is created with structure and data copied from Students
**[CORRECT]**

C. Only the table structure is copied, no data

D. The Students table is renamed to NewStudents

Correct Answer: B

Rationale: CREATE TABLE...AS SELECT (CTAS) creates a new table with both the structure
and data from the source table. Distractor A is incorrect as this is standard SQL. Distractor C
would require additional syntax like WHERE 1=0. Distractor D describes RENAME TABLE.

Question 9

Which data type should be used to store the CourseCode 'D427'?

A. INT

B. CHAR(4) **[CORRECT]**

C. DATE

D. DECIMAL(4,0)

Correct Answer: B