WGU D426 V2 Questions and Answers
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What is a transaction in the context of a database?
A transaction is a sequence of database operations that are treated as a single unit, ensuring
that all operations are completed successfully or none at all, to maintain data integrity.
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What is a transaction in the context of a database?
✔✔ A transaction is a sequence of database operations that are treated as a single unit, ensuring
that all operations are completed successfully or none at all, to maintain data integrity.
What are ACID properties in database management?
✔✔ ACID properties—Atomicity, Consistency, Isolation, Durability—ensure that database
transactions are processed reliably and maintain data integrity even in the event of failure.
What is data redundancy, and why should it be minimized in databases?
✔✔ Data redundancy is the unnecessary duplication of data across a database. It should be
minimized to save storage space, reduce inconsistencies, and improve data management
efficiency.
What is the purpose of a foreign key constraint in a relational database?
✔✔ A foreign key constraint ensures referential integrity by linking a column in one table to the
primary key of another, enforcing relationships between tables.
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,What is the difference between a clustered and a non-clustered index?
✔✔ A clustered index determines the physical order of data in a table and is limited to one per
table, while a non-clustered index creates a separate structure for quick lookups and can have
multiple indexes.
What is the role of a data dictionary in a database?
✔✔ A data dictionary is a centralized repository of metadata that describes the structure,
relationships, and rules governing the data in a database.
What is an inner join, and when would you use it?
✔✔ An inner join retrieves records that have matching values in both tables being joined,
typically used when you want to combine rows that have related data in two or more tables.
What is a weak entity in a database model?
✔✔ A weak entity is one that cannot be uniquely identified by its attributes alone and relies on a
foreign key relationship to a strong entity to establish its identity.
What is a composite attribute in an entity-relationship model?
2
,✔✔ A composite attribute is an attribute that can be divided into smaller subparts, each
representing a more detailed characteristic of the entity.
What is database denormalization, and when might it be used?
✔✔ Denormalization is the process of intentionally introducing redundancy into a database to
improve performance, typically used in scenarios where quick read access is more important than
minimizing storage.
What are the advantages of using a relational database management system (RDBMS)?
✔✔ RDBMS provides data integrity, supports complex queries, allows multiple users to access
data simultaneously, and ensures consistent data storage through normalization and relationships.
What is the difference between DELETE and TRUNCATE in SQL?
✔✔ DELETE removes rows from a table based on a condition and can be rolled back, while
TRUNCATE quickly removes all rows from a table without the option to roll back, but keeps the
table structure intact.
How does database normalization affect query performance?
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, ✔✔ Normalization reduces redundancy and improves data consistency but may increase the
complexity of queries due to the need to join multiple tables, which can slow down performance
in some cases.
What is the role of an SQL trigger?
✔✔ An SQL trigger is a set of instructions that automatically executes in response to certain
events on a table, such as insertions, updates, or deletions, used to enforce business rules or log
changes.
What is data normalization in database design?
✔✔ Data normalization is the process of organizing data in a database to reduce redundancy and
improve data integrity by dividing data into related tables.
Why is database indexing important?
✔✔ Database indexing improves the speed and efficiency of data retrieval by creating a
structured, accessible path for database queries.
What is the difference between a primary key and a foreign key?
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