WGU D426 EXAM 300 ACTUAL QUESTIONS AND CORRECT ANSWERS WITH DETAILED RATIONALES

WGU D426 EXAM 300 ACTUAL QUESTIONS
AND CORRECT ANSWERS WITH DETAILED
RATIONALES


Question 1
What is the primary purpose of a Database Management System (DBMS)?
A) To manage the operating system's file structure
B) To provide a systematic way to create, retrieve, update, and manage data
C) To design web page layouts
D) To compile programming code
Correct Answer: B
Rationale: A DBMS is software that interacts with end-users, applications, and the
database itself to capture and analyze data, providing systematic data
management.


Question 2
Which of the following best describes data independence?
A) The ability to modify the database schema without affecting the DBMS
B) The ability to change the physical storage without rewriting the application
C) The ability to store data without using primary keys
D) The isolation of data from user access
Correct Answer: B

,Rationale: Data independence refers to the immunity of application programs to
changes in the physical storage and access methods.


Question 3
Which type of database model stores data in tables consisting of rows and
columns?
A) Hierarchical
B) Network
C) Relational
D) Object-oriented
Correct Answer: C
Rationale: The relational model organizes data into relations (tables) with tuples
(rows) and attributes (columns).


Question 4
What is a primary key?
A) A key that allows null values
B) A foreign key used for joins
C) A unique identifier for each row in a table
D) A key that references another table
Correct Answer: C
Rationale: A primary key uniquely identifies each record in a database table and
cannot contain NULL values.


Question 5

,What is a foreign key?
A) A key that is the primary key of the same table
B) A field in one table that refers to the primary key of another table
C) A key that allows for duplicate entries
D) A key used for indexing only
Correct Answer: B
Rationale: A foreign key is a column or set of columns in one table that establishes a
link to the primary key or a unique key in another table.


Question 6
What is the primary function of the SQL SELECT statement?
A) To insert new records
B) To delete tables
C) To query and retrieve data from the database
D) To update existing records
Correct Answer: C
Rationale: The SELECT statement is used to select data from a database and return
it as a result set.


Question 7
What does the WHERE clause do in a SQL query?
A) It groups the results
B) It filters rows based on a condition
C) It sorts the results

, D) It joins two tables
Correct Answer: B
Rationale: The WHERE clause specifies criteria that each row must meet to be
included in the result set, effectively filtering the data.


Question 8
Which of the following is a valid SQL aggregate function?
A) SUM()
B) CONCAT()
C) LENGTH()
D) SUBSTRING()
Correct Answer: A
Rationale: SUM() is an aggregate function that calculates the total sum of a numeric
column. CONCAT, LENGTH, and SUBSTRING are string functions.


Question 9
What is the difference between the DELETE and TRUNCATE commands?
A) DELETE is faster for large tables
B) TRUNCATE logs individual row deletions
C) DELETE can have a WHERE clause; TRUNCATE cannot
D) There is no difference
Correct Answer: C
Rationale: DELETE allows conditional row removal via WHERE, while TRUNCATE
removes all rows without conditions.