WGU D427 DATA MANAGEMENT APPLICATIONS OA EXAM AND STUDY GUIDE LATEST 2025 | PRACTICE QUESTIONS AND ANSWERS | EXAM REVIEW | VERIFIED SOLUTIONS

WGU D427 DATA MANAGEMENT APPLICATIONS OA
EXAM AND STUDY GUIDE LATEST 2025 | PRACTICE
QUESTIONS AND ANSWERS | EXAM REVIEW |
VERIFIED SOLUTIONS


1. In relational database terminology, a tuple is equivalent to:
A) A column
B) A row
C) A table
D) A primary key
Correct Answer: B
A tuple is a single row or record in a relation (table). An attribute is a column; a
relation is a table; a primary key is a column or column set that uniquely identifies
tuples.
2. Which SQL command is used to remove a table and all its data
permanently?
A) DELETE TABLE
B) DROP TABLE
C) TRUNCATE TABLE
D) REMOVE TABLE
Correct Answer: B
DROP TABLE removes the table structure and data from the database. DELETE
removes rows but leaves the table; TRUNCATE removes all rows quickly but leaves
the table structure; REMOVE TABLE is not a standard SQL command.
3. Which of the following is NOT a characteristic of a primary key?
A) It must be unique.
B) It cannot contain NULLs.
C) It can be composite.
D) It must be a foreign key in another table.

,Correct Answer: D
A primary key may be referenced by a foreign key in another table, but it does not
have to be. It must be unique and non-NULL, and it may consist of multiple
columns (composite key).
4. Which SQL clause is used to filter rows after they have been grouped?
A) WHERE
B) GROUP BY
C) HAVING
D) ORDER BY
Correct Answer: C
HAVING filters groups after GROUP BY; WHERE filters individual rows before
grouping. ORDER BY sorts the result set.
5. In an ER diagram, a many-to-many relationship between Student and
Course is usually implemented by:
A) Adding a foreign key to Student referencing Course
B) Adding a foreign key to Course referencing Student
C) Creating an associative (junction) table with foreign keys to both
D) Merging the two tables
Correct Answer: C
Many-to-many relationships require an associative table containing foreign keys
referencing both entities, often along with attributes describing the relationship
(e.g., enrollment date).
6. Which normal form is violated if a non-key column depends on only part of
a composite primary key?
A) 1NF
B) 2NF
C) 3NF
D) BCNF
Correct Answer: B
Second normal form requires that all non-key attributes depend on the whole

,composite primary key, not just part of it. Partial dependency violates 2NF. 1NF
concerns atomic values; 3NF concerns transitive dependencies.
7. In SQL, which statement changes the data type of a column?
A) UPDATE COLUMN
B) MODIFY COLUMN
C) ALTER TABLE ... ALTER COLUMN or MODIFY
D) CHANGE DATA TYPE
Correct Answer: C
ALTER TABLE with ALTER COLUMN (SQL Server) or MODIFY (MySQL/Oracle)
changes a column's data type. UPDATE changes data values; the other options are
not standard SQL commands.
8. Which join returns all rows from the left table and matching rows from the
right table, with NULLs for non-matching right rows?
A) INNER JOIN
B) RIGHT JOIN
C) LEFT JOIN
D) CROSS JOIN
Correct Answer: C
LEFT JOIN (LEFT OUTER JOIN) includes all rows from the left table and only
matching rows from the right table. RIGHT JOIN is opposite; INNER JOIN only
matching rows; CROSS JOIN produces Cartesian product.
9. Which SQL aggregate function counts all rows including NULLs?
A) COUNT(*)
B) COUNT(column)
C) SUM(column)
D) AVG(column)
Correct Answer: A
COUNT() counts all rows, regardless of NULLs. COUNT(column) ignores NULL
values in that column. SUM and AVG ignore NULLs and are for numeric values.*

, 10.A foreign key constraint enforces:
A) Entity integrity
B) Referential integrity
C) Domain integrity
D) User-defined integrity
Correct Answer: B
Referential integrity ensures that a foreign key value matches a primary key value
in the referenced table or is NULL (if allowed). Entity integrity is about primary
keys being unique/non-NULL; domain integrity concerns allowed values; user-
defined integrity is custom rules.
11.In SQL, which command removes all rows from a table but retains the table
structure and does not log individual row deletions?
A) DELETE
B) DROP
C) TRUNCATE
D) REMOVE
Correct Answer: C
TRUNCATE removes all rows quickly and often cannot be rolled back (DBMS-
dependent), while DELETE removes rows row-by-row and can include WHERE.
DROP removes the entire table. REMOVE is not standard.
12.Which SQL keyword is used to sort result rows in descending order?
A) SORT DESC
B) ORDER BY column DESC
C) GROUP BY DESC
D) SORTING DESC
Correct Answer: B
ORDER BY column DESC sorts the result in descending order. ORDER BY ASC is
ascending (default). The other options are not standard SQL clauses.
13.Which data type is appropriate for storing a large block of text such as an
article?