WGU C170: Data Management
Applications Final Examination
Questions And Answers With
Rationales/Graded A+/2026 Update/100%
Correct /Instant Download
Section 1: Relational Algebra & Database Foundations (Questions 1-10)
1. A property of relational operators that allows you to use the output of one
operation as the input for another operation is known as:
A) Functional Dependency
B) Closure
C) Cardinality
D) Selectivity
Correct Answer: B) Closure
Rationale: Closure is the fundamental property that allows relational algebra
operations (like SELECT, PROJECT, JOIN) to be nested. Because the result of a
relational operation is always another relation (table), it can be passed as an input
to another operation . Option A defines relationships between attributes, C defines
counts in relationships, and D is a query optimization metric.
2. Which relational algebra operator would you use to find all rows that exist
in Table A but not in Table B, assuming both tables are union-compatible?
A) UNION
B) INTERSECT
C) DIFFERENCE (MINUS)
D) PRODUCT
Correct Answer: C) DIFFERENCE (MINUS)
Rationale: The DIFFERENCE operator (often called MINUS or EXCEPT in SQL)
returns rows from the first query that are not present in the second. UNION merges
rows, INTERSECT returns common rows, and PRODUCT creates a Cartesian
combination .
,3. In relational set theory, what must be true for two tables to be considered
"union-compatible"?
A) They must have a foreign key relationship
B) They must have the same number of attributes and corresponding compatible
domains
C) They must have the exact same data in every row
D) They must be normalized to 3NF
Correct Answer: B) They must have the same number of attributes and
corresponding compatible domains
Rationale: Union-compatibility is a strict structural requirement. The tables must
have the same degree (number of columns) and the data types of corresponding
columns must be compatible so that UNION, INTERSECT, or DIFFERENCE
operations make logical sense .
4. Which join operation returns the Cartesian product of two tables?
A) Natural Join
B) Equijoin
C) Cross Join
D) Outer Join
Correct Answer: C) Cross Join
Rationale: A CROSS JOIN (or Cartesian Product) pairs every row from the first
table with every row from the second table. If Table A has 5 rows and Table B has
10 rows, the result is 50 rows . Natural and Equijoins include a condition; Outer
Joins preserve unmatched rows.
5. Which of the following best describes a "Superkey"?
A) A key that is used to index a view
B) A subset of a candidate key
C) An attribute or set of attributes that uniquely identifies each entity in a table
D) A key that contains null values
Correct Answer: C) An attribute or set of attributes that uniquely identifies
each entity in a table
Rationale: A superkey is any combination of columns that guarantees uniqueness.
It can contain extra attributes. A Candidate Key is a minimal superkey (no subset
of it is also a superkey) .
, 6. The "RESTRICT" operation in relational algebra is equivalent to which
SQL clause?
A) SELECT (the FROM clause)
B) SELECT (the WHERE clause)
C) PROJECT
D) JOIN
Correct Answer: B) SELECT (the WHERE clause)
Rationale: In relational algebra, RESTRICT (or SELECT, though naming varies)
filters rows based on a predicate. In SQL, the WHERE clause serves this row-
filtering purpose. PROJECT filters columns .
7. A join that uses an inequality comparison operator (e.g., < or >) in the join
condition is specifically known as a:
A) Equijoin
B) Natural join
C) Theta join
D) Self-join
Correct Answer: C) Theta join
Rationale: Theta joins are the general case of joins that use a comparison
operator. If the operator is "=", it is an Equijoin. If it also removes duplicate
columns, it is a Natural Join .
8. What does the "DIVIDE" operator accomplish in relational algebra?
A) It splits a table into two vertical partitions
B) It answers queries about "for all" or "one set associated with all values of
another set"
C) It divides numeric columns by a constant
D) It splits a union-compatible table into two halves
Correct Answer: B) It answers queries about "for all" or "one set associated
with all values of another set"
Rationale: The DIVIDE operator is highly specialized. It is used for queries like
"Find students who have enrolled in all available courses." It answers questions
involving universal quantification .
9. Which of the following is a characteristic of a "Natural Join"?
A) It includes all rows from the left table regardless of matches
B) It uses the ON clause to specify matching columns
Applications Final Examination
Questions And Answers With
Rationales/Graded A+/2026 Update/100%
Correct /Instant Download
Section 1: Relational Algebra & Database Foundations (Questions 1-10)
1. A property of relational operators that allows you to use the output of one
operation as the input for another operation is known as:
A) Functional Dependency
B) Closure
C) Cardinality
D) Selectivity
Correct Answer: B) Closure
Rationale: Closure is the fundamental property that allows relational algebra
operations (like SELECT, PROJECT, JOIN) to be nested. Because the result of a
relational operation is always another relation (table), it can be passed as an input
to another operation . Option A defines relationships between attributes, C defines
counts in relationships, and D is a query optimization metric.
2. Which relational algebra operator would you use to find all rows that exist
in Table A but not in Table B, assuming both tables are union-compatible?
A) UNION
B) INTERSECT
C) DIFFERENCE (MINUS)
D) PRODUCT
Correct Answer: C) DIFFERENCE (MINUS)
Rationale: The DIFFERENCE operator (often called MINUS or EXCEPT in SQL)
returns rows from the first query that are not present in the second. UNION merges
rows, INTERSECT returns common rows, and PRODUCT creates a Cartesian
combination .
,3. In relational set theory, what must be true for two tables to be considered
"union-compatible"?
A) They must have a foreign key relationship
B) They must have the same number of attributes and corresponding compatible
domains
C) They must have the exact same data in every row
D) They must be normalized to 3NF
Correct Answer: B) They must have the same number of attributes and
corresponding compatible domains
Rationale: Union-compatibility is a strict structural requirement. The tables must
have the same degree (number of columns) and the data types of corresponding
columns must be compatible so that UNION, INTERSECT, or DIFFERENCE
operations make logical sense .
4. Which join operation returns the Cartesian product of two tables?
A) Natural Join
B) Equijoin
C) Cross Join
D) Outer Join
Correct Answer: C) Cross Join
Rationale: A CROSS JOIN (or Cartesian Product) pairs every row from the first
table with every row from the second table. If Table A has 5 rows and Table B has
10 rows, the result is 50 rows . Natural and Equijoins include a condition; Outer
Joins preserve unmatched rows.
5. Which of the following best describes a "Superkey"?
A) A key that is used to index a view
B) A subset of a candidate key
C) An attribute or set of attributes that uniquely identifies each entity in a table
D) A key that contains null values
Correct Answer: C) An attribute or set of attributes that uniquely identifies
each entity in a table
Rationale: A superkey is any combination of columns that guarantees uniqueness.
It can contain extra attributes. A Candidate Key is a minimal superkey (no subset
of it is also a superkey) .
, 6. The "RESTRICT" operation in relational algebra is equivalent to which
SQL clause?
A) SELECT (the FROM clause)
B) SELECT (the WHERE clause)
C) PROJECT
D) JOIN
Correct Answer: B) SELECT (the WHERE clause)
Rationale: In relational algebra, RESTRICT (or SELECT, though naming varies)
filters rows based on a predicate. In SQL, the WHERE clause serves this row-
filtering purpose. PROJECT filters columns .
7. A join that uses an inequality comparison operator (e.g., < or >) in the join
condition is specifically known as a:
A) Equijoin
B) Natural join
C) Theta join
D) Self-join
Correct Answer: C) Theta join
Rationale: Theta joins are the general case of joins that use a comparison
operator. If the operator is "=", it is an Equijoin. If it also removes duplicate
columns, it is a Natural Join .
8. What does the "DIVIDE" operator accomplish in relational algebra?
A) It splits a table into two vertical partitions
B) It answers queries about "for all" or "one set associated with all values of
another set"
C) It divides numeric columns by a constant
D) It splits a union-compatible table into two halves
Correct Answer: B) It answers queries about "for all" or "one set associated
with all values of another set"
Rationale: The DIVIDE operator is highly specialized. It is used for queries like
"Find students who have enrolled in all available courses." It answers questions
involving universal quantification .
9. Which of the following is a characteristic of a "Natural Join"?
A) It includes all rows from the left table regardless of matches
B) It uses the ON clause to specify matching columns
