Free DMC Techniques and Methodologies Questions and Answers — Questions and Answers
Question 1: Which of the following are key objectives of normalization in data modeling?
- Reducing data redundancy (Correct answer)
- Enhancing database security
- Improving data integrity (Correct answer)
- Increasing query execution speed
Correct answer: Reducing data redundancy
Normalization in data modeling aims to organize database tables to minimize data redundancy and improve data integrity. By breaking down large tables into smaller, related ones, it ensures that data is stored only once, reducing storage space and preventing inconsistencies. This structured approach helps maintain the accuracy and reliability of the data.
Question 2: Which of the following best describes the star schema used in dimensional modeling?
- It contains normalized tables with minimal redundancy.
- It uses a central fact table surrounded by dimension tables. (Correct answer)
- It is used exclusively for transactional systems.
- It has no foreign key relationships between tables.
Correct answer: It uses a central fact table surrounded by dimension tables.
The star schema is a foundational structure in dimensional modeling, commonly used in data warehouses for analytical purposes. It consists of a central 'fact' table, which contains quantitative measures, surrounded by multiple 'dimension' tables that provide descriptive context for those measures. This simple, denormalized structure optimizes query performance for reporting and business intelligence.
Question 3: What is the primary key in a relational database?
- A unique identifier for a row in a table. (Correct answer)
- A column or set of columns that ensures referential integrity.
- A field used to link two tables together.
- A column that must contain unique and non-null values. (Correct answer)
Correct answer: A unique identifier for a row in a table.
A primary key is a crucial component in relational databases, serving as a unique identifier for each record (row) within a table. It ensures that every row can be distinctly identified and accessed, preventing duplicate entries. By definition, a primary key must contain unique and non-null values, guaranteeing data integrity and enabling relationships with other tables through foreign keys.
Question 4: Which of the following best describes denormalization?
- A process of increasing table normalization to 5NF or higher.
- A technique used to optimize read performance by combining tables. (Correct answer)
- The act of restructuring databases to eliminate foreign keys.
- A process used exclusively in NoSQL databases.
Correct answer: A technique used to optimize read performance by combining tables.
Denormalization is a database optimization technique where redundant data is intentionally added to a normalized database, or tables are combined, to improve read performance. While it increases data redundancy, it reduces the number of joins required for complex queries, making data retrieval faster. This approach is often employed in data warehousing and reporting systems where read speed is prioritized over strict normalization.
Question 5: Which of the following are common elements of an Entity-Relationship Diagram (ERD)?
- Entities (Correct answer)
- Attributes (Correct answer)
- Keys (Primary and Foreign) (Correct answer)
- Data Pipelines
Correct answer: Entities
An Entity-Relationship Diagram (ERD) is a visual tool used to model the structure of a database. Its common elements include entities, which represent real-world objects; attributes, which describe the properties of an entity; and relationships, which show how entities are connected. Keys, such as primary and foreign keys, are essential attributes that define these relationships and ensure data integrity.
Free DMC Techniques and Methodologies Questions and Answers
Which of the following are key objectives of normalization in data modeling?