1
WGU D427 Data Management
Applications OA Exam 2025 – 400
Verified Questions & Answers | 100%
Accurate | A+ Grade
Data Modeling and Database Design
1. What is the primary purpose of a database model in a relational database system?
A) To store data in a hierarchical structure
B) To define how data is organized, manipulated, and validated
C) To manage network connections between servers
D) To provide a user interface for data entry
B) To define how data is organized, manipulated, and validated
Rationale: A database model, such as the relational model, provides a framework for
structuring data (tables, columns), defining operations (e.g., SQL queries), and enforcing
rules (e.g., constraints) to ensure data integrity.
2. Which component of a database model prescribes how data is organized?
A) Operations
B) Constraints
C) Data structures
D) Queries
C) Data structures
Rationale: Data structures, such as tables, columns, and rows, define the organization of
data in a database model, specifying how data is stored and related.
3. In the relational model, what is a tuple?
A) An unordered collection of elements
B) A named set of values
C) An ordered collection of elements
D) A database constraint
C) An ordered collection of elements
Rationale: A tuple is an ordered collection of elements (values) in a relational database,
typically represented as a row in a table, with each value corresponding to a column.
4. What does the term "domain" refer to in the context of a relational database?
A) A set of allowed values for a column
B) A unique identifier for a table
C) A relationship between two tables
D) A query execution plan
A) A set of allowed values for a column
Rationale: In a relational database, a domain is a set of permissible values for a column’s
data type, ensuring that only valid data is stored.
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5. Which database model organizes data into tables with rows and columns?
A) Hierarchical model
B) Network model
C) Relational model
D) NoSQL model
C) Relational model
Rationale: The relational model, introduced by E.F. Codd, uses tables (relations) with
rows (tuples) and columns (attributes) to organize data, standardized by SQL.
6. What is the purpose of a schema in a database?
A) To execute SQL queries
B) To define the structure and organization of the database
C) To manage user permissions
D) To store temporary data
B) To define the structure and organization of the database
Rationale: A schema defines the structure of the database, including tables, columns,
data types, and relationships, serving as a blueprint for data organization.
7. Which of the following is NOT a component of a database model?
A) Data structures
B) Operations
C) Constraints
D) User interface
D) User interface
Rationale: A database model includes data structures, operations, and constraints, but the
user interface is not part of the model—it is part of the application layer.
8. What is a key characteristic of a relational database table?
A) Duplicate rows are allowed
B) Columns must have unique names
C) Rows are unordered sets
D) Tables cannot have primary keys
B) Columns must have unique names
Rationale: In a relational database, each column in a table must have a unique name to
avoid ambiguity when referencing attributes in queries or operations.
9. In relational algebra, which operation selects a subset of rows from a table?
A) Project
B) Join
C) Select
D) Union
C) Select
Rationale: The Select operation in relational algebra filters rows from a table based on a
condition, returning a subset of rows that meet the criteria.
10. Which relational algebra operation eliminates one or more columns from a table?
A) Select
B) Project
C) Join
D) Union
B) Project
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Rationale: The Project operation in relational algebra selects specific columns from a
table, effectively eliminating others, while retaining all rows.
11. What does the relational algebra "Join" operation do?
A) Combines rows from two tables based on a condition
B) Selects a subset of rows from a single table
C) Removes duplicate rows from a table
D) Merges two tables without conditions
A) Combines rows from two tables based on a condition
Rationale: The Join operation combines rows from two tables based on a matching
condition, typically involving related columns like foreign keys.
12. Which relational algebra operation combines all rows from two tables?
A) Union
B) Intersect
C) Product
D) Difference
C) Product
Rationale: The Product operation (Cartesian product) combines all rows from two tables,
creating a new table with all possible row combinations.
13. What is the result of the relational algebra Union operation?
A) Rows common to two tables
B) All rows from both tables, with duplicates removed
C) Rows in one table but not in another
D) A subset of columns from both tables
B) All rows from both tables, with duplicates removed
Rationale: The Union operation combines all rows from two tables, eliminating
duplicates to produce a single table with unique rows.
14. Which relational algebra operation selects rows common to two tables?
A) Union
B) Intersect
C) Difference
D) Project
B) Intersect
Rationale: The Intersect operation returns only the rows that appear in both input tables,
based on matching values.
15. What does the relational algebra Difference operation do?
A) Combines all rows from two tables
B) Returns rows in one table but not in another
C) Selects common rows from two tables
D) Renames a table
B) Returns rows in one table but not in another
Rationale: The Difference operation returns rows that exist in one table but not in
another, useful for finding unique records.
16. What is the purpose of the Rename operation in relational algebra?
A) To modify column values
B) To change a table’s name
C) To join two tables
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D) To delete rows
B) To change a table’s name
Rationale: The Rename operation changes the name of a table or its attributes, often used
to avoid naming conflicts in queries.
17. Which operation in relational algebra computes functions like sum or count?
A) Select
B) Project
C) Aggregate
D) Join
C) Aggregate
Rationale: The Aggregate operation computes functions (e.g., SUM, COUNT, AVG)
over multiple rows, typically grouping data by specific columns.
18. What is a key feature of the relational model?
A) Allows duplicate rows
B) Enforces unique column names
C) Stores data in a tree structure
D) Uses non-tabular data structures
B) Enforces unique column names
Rationale: The relational model requires unique column names within a table to ensure
clarity and prevent ambiguity in queries.
19. In a database, what is a set?
A) An ordered collection of elements
B) An unordered collection of elements
C) A named column in a table
D) A primary key constraint
B) An unordered collection of elements
Rationale: A set in a database is an unordered collection of elements, such as rows in a
table, where order does not matter.
20. What is the role of business rules in a database?
A) To define the structure of the database
B) To enforce organization-specific policies
C) To execute SQL queries
D) To manage hardware resources
B) To enforce organization-specific policies
Rationale: Business rules are specific to an organization’s policies and are implemented
as constraints or triggers to enforce data consistency.
Entity-Relationship Diagrams (ERDs)
21. What does an Entity-Relationship Diagram (ERD) represent?
A) Database performance metrics
B) Relationships between entities in a database
C) SQL query execution plans
D) Hardware configurations
B) Relationships between entities in a database
WGU D427 Data Management
Applications OA Exam 2025 – 400
Verified Questions & Answers | 100%
Accurate | A+ Grade
Data Modeling and Database Design
1. What is the primary purpose of a database model in a relational database system?
A) To store data in a hierarchical structure
B) To define how data is organized, manipulated, and validated
C) To manage network connections between servers
D) To provide a user interface for data entry
B) To define how data is organized, manipulated, and validated
Rationale: A database model, such as the relational model, provides a framework for
structuring data (tables, columns), defining operations (e.g., SQL queries), and enforcing
rules (e.g., constraints) to ensure data integrity.
2. Which component of a database model prescribes how data is organized?
A) Operations
B) Constraints
C) Data structures
D) Queries
C) Data structures
Rationale: Data structures, such as tables, columns, and rows, define the organization of
data in a database model, specifying how data is stored and related.
3. In the relational model, what is a tuple?
A) An unordered collection of elements
B) A named set of values
C) An ordered collection of elements
D) A database constraint
C) An ordered collection of elements
Rationale: A tuple is an ordered collection of elements (values) in a relational database,
typically represented as a row in a table, with each value corresponding to a column.
4. What does the term "domain" refer to in the context of a relational database?
A) A set of allowed values for a column
B) A unique identifier for a table
C) A relationship between two tables
D) A query execution plan
A) A set of allowed values for a column
Rationale: In a relational database, a domain is a set of permissible values for a column’s
data type, ensuring that only valid data is stored.
, 2
5. Which database model organizes data into tables with rows and columns?
A) Hierarchical model
B) Network model
C) Relational model
D) NoSQL model
C) Relational model
Rationale: The relational model, introduced by E.F. Codd, uses tables (relations) with
rows (tuples) and columns (attributes) to organize data, standardized by SQL.
6. What is the purpose of a schema in a database?
A) To execute SQL queries
B) To define the structure and organization of the database
C) To manage user permissions
D) To store temporary data
B) To define the structure and organization of the database
Rationale: A schema defines the structure of the database, including tables, columns,
data types, and relationships, serving as a blueprint for data organization.
7. Which of the following is NOT a component of a database model?
A) Data structures
B) Operations
C) Constraints
D) User interface
D) User interface
Rationale: A database model includes data structures, operations, and constraints, but the
user interface is not part of the model—it is part of the application layer.
8. What is a key characteristic of a relational database table?
A) Duplicate rows are allowed
B) Columns must have unique names
C) Rows are unordered sets
D) Tables cannot have primary keys
B) Columns must have unique names
Rationale: In a relational database, each column in a table must have a unique name to
avoid ambiguity when referencing attributes in queries or operations.
9. In relational algebra, which operation selects a subset of rows from a table?
A) Project
B) Join
C) Select
D) Union
C) Select
Rationale: The Select operation in relational algebra filters rows from a table based on a
condition, returning a subset of rows that meet the criteria.
10. Which relational algebra operation eliminates one or more columns from a table?
A) Select
B) Project
C) Join
D) Union
B) Project
, 3
Rationale: The Project operation in relational algebra selects specific columns from a
table, effectively eliminating others, while retaining all rows.
11. What does the relational algebra "Join" operation do?
A) Combines rows from two tables based on a condition
B) Selects a subset of rows from a single table
C) Removes duplicate rows from a table
D) Merges two tables without conditions
A) Combines rows from two tables based on a condition
Rationale: The Join operation combines rows from two tables based on a matching
condition, typically involving related columns like foreign keys.
12. Which relational algebra operation combines all rows from two tables?
A) Union
B) Intersect
C) Product
D) Difference
C) Product
Rationale: The Product operation (Cartesian product) combines all rows from two tables,
creating a new table with all possible row combinations.
13. What is the result of the relational algebra Union operation?
A) Rows common to two tables
B) All rows from both tables, with duplicates removed
C) Rows in one table but not in another
D) A subset of columns from both tables
B) All rows from both tables, with duplicates removed
Rationale: The Union operation combines all rows from two tables, eliminating
duplicates to produce a single table with unique rows.
14. Which relational algebra operation selects rows common to two tables?
A) Union
B) Intersect
C) Difference
D) Project
B) Intersect
Rationale: The Intersect operation returns only the rows that appear in both input tables,
based on matching values.
15. What does the relational algebra Difference operation do?
A) Combines all rows from two tables
B) Returns rows in one table but not in another
C) Selects common rows from two tables
D) Renames a table
B) Returns rows in one table but not in another
Rationale: The Difference operation returns rows that exist in one table but not in
another, useful for finding unique records.
16. What is the purpose of the Rename operation in relational algebra?
A) To modify column values
B) To change a table’s name
C) To join two tables
, 4
D) To delete rows
B) To change a table’s name
Rationale: The Rename operation changes the name of a table or its attributes, often used
to avoid naming conflicts in queries.
17. Which operation in relational algebra computes functions like sum or count?
A) Select
B) Project
C) Aggregate
D) Join
C) Aggregate
Rationale: The Aggregate operation computes functions (e.g., SUM, COUNT, AVG)
over multiple rows, typically grouping data by specific columns.
18. What is a key feature of the relational model?
A) Allows duplicate rows
B) Enforces unique column names
C) Stores data in a tree structure
D) Uses non-tabular data structures
B) Enforces unique column names
Rationale: The relational model requires unique column names within a table to ensure
clarity and prevent ambiguity in queries.
19. In a database, what is a set?
A) An ordered collection of elements
B) An unordered collection of elements
C) A named column in a table
D) A primary key constraint
B) An unordered collection of elements
Rationale: A set in a database is an unordered collection of elements, such as rows in a
table, where order does not matter.
20. What is the role of business rules in a database?
A) To define the structure of the database
B) To enforce organization-specific policies
C) To execute SQL queries
D) To manage hardware resources
B) To enforce organization-specific policies
Rationale: Business rules are specific to an organization’s policies and are implemented
as constraints or triggers to enforce data consistency.
Entity-Relationship Diagrams (ERDs)
21. What does an Entity-Relationship Diagram (ERD) represent?
A) Database performance metrics
B) Relationships between entities in a database
C) SQL query execution plans
D) Hardware configurations
B) Relationships between entities in a database
