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WGU D426 DATA MANAGEMENT
FOUNDATIONS – SQL & DATABASE DESIGN
STUDY GUIDE | LATEST UPDATE 2026/2027 |
PRACTICE QUESTIONS AND ANSWERS |
EXAM REVIEW
Table of Contents
1. Relational Model, Keys, and Integrity Constraints
2. Entity-Relationship Modeling and Database Design
3. Normalization and Logical Design
4. SQL Data Definition Language (DDL)
5. SQL Data Manipulation Language (DML) and Queries
6. Joins, Subqueries, Set Operators, and Functions
7. Views, Indexes, and Performance Optimization
8. Transactions, Concurrency, and Recovery
9. Stored Programs, Triggers, and Security
10. Data Warehousing, OLAP, NoSQL, and Distributed Databases
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Question 1: In the relational model, which key is chosen from candidate keys to uniquely
identify each row in a relation and cannot contain NULL values?
A) Foreign key
B) Alternate key
C) Primary key
D) Superkey
Correct Answer: C) Primary key
A primary key is the candidate key selected by the designer to be the principal unique
identifier for each tuple in a relation. It enforces entity integrity by requiring uniqueness and
disallowing NULL values.
Question 2: A foreign key in a child table references the primary key of a parent table. If a
child row contains a foreign key value that does not exist in the parent table, which integrity
constraint is violated?
A) Entity integrity
B) Referential integrity
C) Domain integrity
D) Semantic integrity
Correct Answer: B) Referential integrity
Referential integrity ensures that a foreign key value must either match an existing primary
key value in the referenced table or be NULL, depending on the constraint. A nonmatching
non-NULL value violates this rule.
Question 3: A table has columns StudentID, Email, and Phone. Both StudentID and Email
can uniquely identify a student, but StudentID is selected as the primary key. What is Email
in this design?
A) Foreign key
B) Alternate key
C) Composite key
D) Surrogate key
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Correct Answer: B) Alternate key
An alternate key is any candidate key not chosen as the primary key. Since Email can
uniquely identify a student but was not selected as the primary key, it is an alternate key.
Question 4: Which constraint ensures that a primary key column cannot contain NULL
values?
A) Referential integrity
B) Entity integrity
C) Domain integrity
D) Business integrity
Correct Answer: B) Entity integrity
Entity integrity requires that every relation have a primary key and that primary key values
be unique and not NULL. This ensures each row can be uniquely identified.
Question 5: A database designer specifies ON DELETE CASCADE for a foreign key. What
happens when a parent row is deleted?
A) The delete is rejected if child rows exist.
B) The foreign key values in child rows are set to NULL.
C) The corresponding child rows are automatically deleted.
D) The parent row is deleted and child rows remain unchanged.
Correct Answer: C) The corresponding child rows are automatically deleted.
ON DELETE CASCADE propagates the delete operation from the parent table to matching
child rows. This maintains referential integrity by removing dependent rows automatically.
Question 6: In an entity-relationship diagram, a relationship between two entities where one
entity instance can relate to many instances of the other, and vice versa, is represented as:
A) 1:1
B) 1:M
C) M:N
D) Unary
Correct Answer: C) M:N
A many-to-many relationship exists when multiple instances of one entity relate to multiple
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instances of another. In relational design, it is typically resolved with an associative or
junction table.
Question 7: Which ER construct is used to represent an entity that cannot exist independently
of another entity and has no unique identifier of its own?
A) Strong entity
B) Weak entity
C) Associative entity
D) Supertype entity
Correct Answer: B) Weak entity
A weak entity depends on a strong owner entity for its existence and identity. It typically has a
partial key and is identified through its relationship with the owner entity.
Question 8: A many-to-many relationship between Student and Course is converted into
relational tables. What is the most appropriate design?
A) Add CourseID as a foreign key in Student.
B) Add StudentID as a foreign key in Course.
C) Create a new associative table with StudentID and CourseID as a composite key.
D) Merge Student and Course into one table.
Correct Answer: C) Create a new associative table with StudentID and CourseID as a
composite key.
An associative table resolves the M:N relationship by storing each valid pairing of Student
and Course. The combination of StudentID and CourseID uniquely identifies each enrollment
row.
Question 9: A relation is in first normal form (1NF) when:
A) It has no partial dependencies.
B) It has no transitive dependencies.
C) All attributes contain only atomic values and each row is unique.
D) Every determinant is a candidate key.
Correct Answer: C) All attributes contain only atomic values and each row is unique.
First normal form prohibits repeating groups and multivalued attributes within a single
column. Each attribute must hold a single atomic value for each row.
WGU D426 DATA MANAGEMENT
FOUNDATIONS – SQL & DATABASE DESIGN
STUDY GUIDE | LATEST UPDATE 2026/2027 |
PRACTICE QUESTIONS AND ANSWERS |
EXAM REVIEW
Table of Contents
1. Relational Model, Keys, and Integrity Constraints
2. Entity-Relationship Modeling and Database Design
3. Normalization and Logical Design
4. SQL Data Definition Language (DDL)
5. SQL Data Manipulation Language (DML) and Queries
6. Joins, Subqueries, Set Operators, and Functions
7. Views, Indexes, and Performance Optimization
8. Transactions, Concurrency, and Recovery
9. Stored Programs, Triggers, and Security
10. Data Warehousing, OLAP, NoSQL, and Distributed Databases
,2|Page
Question 1: In the relational model, which key is chosen from candidate keys to uniquely
identify each row in a relation and cannot contain NULL values?
A) Foreign key
B) Alternate key
C) Primary key
D) Superkey
Correct Answer: C) Primary key
A primary key is the candidate key selected by the designer to be the principal unique
identifier for each tuple in a relation. It enforces entity integrity by requiring uniqueness and
disallowing NULL values.
Question 2: A foreign key in a child table references the primary key of a parent table. If a
child row contains a foreign key value that does not exist in the parent table, which integrity
constraint is violated?
A) Entity integrity
B) Referential integrity
C) Domain integrity
D) Semantic integrity
Correct Answer: B) Referential integrity
Referential integrity ensures that a foreign key value must either match an existing primary
key value in the referenced table or be NULL, depending on the constraint. A nonmatching
non-NULL value violates this rule.
Question 3: A table has columns StudentID, Email, and Phone. Both StudentID and Email
can uniquely identify a student, but StudentID is selected as the primary key. What is Email
in this design?
A) Foreign key
B) Alternate key
C) Composite key
D) Surrogate key
,3|Page
Correct Answer: B) Alternate key
An alternate key is any candidate key not chosen as the primary key. Since Email can
uniquely identify a student but was not selected as the primary key, it is an alternate key.
Question 4: Which constraint ensures that a primary key column cannot contain NULL
values?
A) Referential integrity
B) Entity integrity
C) Domain integrity
D) Business integrity
Correct Answer: B) Entity integrity
Entity integrity requires that every relation have a primary key and that primary key values
be unique and not NULL. This ensures each row can be uniquely identified.
Question 5: A database designer specifies ON DELETE CASCADE for a foreign key. What
happens when a parent row is deleted?
A) The delete is rejected if child rows exist.
B) The foreign key values in child rows are set to NULL.
C) The corresponding child rows are automatically deleted.
D) The parent row is deleted and child rows remain unchanged.
Correct Answer: C) The corresponding child rows are automatically deleted.
ON DELETE CASCADE propagates the delete operation from the parent table to matching
child rows. This maintains referential integrity by removing dependent rows automatically.
Question 6: In an entity-relationship diagram, a relationship between two entities where one
entity instance can relate to many instances of the other, and vice versa, is represented as:
A) 1:1
B) 1:M
C) M:N
D) Unary
Correct Answer: C) M:N
A many-to-many relationship exists when multiple instances of one entity relate to multiple
, 4|Page
instances of another. In relational design, it is typically resolved with an associative or
junction table.
Question 7: Which ER construct is used to represent an entity that cannot exist independently
of another entity and has no unique identifier of its own?
A) Strong entity
B) Weak entity
C) Associative entity
D) Supertype entity
Correct Answer: B) Weak entity
A weak entity depends on a strong owner entity for its existence and identity. It typically has a
partial key and is identified through its relationship with the owner entity.
Question 8: A many-to-many relationship between Student and Course is converted into
relational tables. What is the most appropriate design?
A) Add CourseID as a foreign key in Student.
B) Add StudentID as a foreign key in Course.
C) Create a new associative table with StudentID and CourseID as a composite key.
D) Merge Student and Course into one table.
Correct Answer: C) Create a new associative table with StudentID and CourseID as a
composite key.
An associative table resolves the M:N relationship by storing each valid pairing of Student
and Course. The combination of StudentID and CourseID uniquely identifies each enrollment
row.
Question 9: A relation is in first normal form (1NF) when:
A) It has no partial dependencies.
B) It has no transitive dependencies.
C) All attributes contain only atomic values and each row is unique.
D) Every determinant is a candidate key.
Correct Answer: C) All attributes contain only atomic values and each row is unique.
First normal form prohibits repeating groups and multivalued attributes within a single
column. Each attribute must hold a single atomic value for each row.
