Scenario: Your team is experiencing slow query performance in a production database. Upon investigation, you find that there are no indexes on the columns frequently used in the WHERE clause of queries. What would be your recommended solution to improve query performance?
- Create Indexes on the frequently used columns
- Increase server memory
- Optimize SQL queries
- Upgrade database hardware
To improve query performance, creating indexes on the columns frequently used in the WHERE clause can significantly reduce the time taken for query execution by allowing the database engine to quickly locate the relevant rows.
In which scenario would you consider using a non-clustered index over a clustered index?
- When you frequently query a large range of values
- When you need to enforce a primary key constraint
- When you need to physically reorder the table data
- When you want to ensure data integrity
A non-clustered index is considered when you frequently query a large range of values or when you want to avoid the overhead of reordering the physical data in the table, which is required by a clustered index.
What are the challenges associated with Data Lake implementation?
- Data integration difficulties
- Ingestion complexities
- Lack of data governance
- Scalability issues
Challenges in Data Lake implementation often include the lack of data governance, which can lead to issues related to data quality, consistency, and compliance. Ensuring proper governance mechanisms is crucial for maintaining the integrity and reliability of data within the Data Lake.
What is the primary purpose of workflow orchestration tools like Apache Airflow and Luigi?
- Creating interactive data visualizations
- Developing machine learning models
- Managing and scheduling complex data workflows
- Storing and querying large datasets
Workflow orchestration tools like Apache Airflow and Luigi are primarily designed to manage and schedule complex data workflows. They allow data engineers to define, schedule, and monitor workflows consisting of multiple tasks or processes, facilitating the automation and orchestration of data pipelines. These tools provide features such as task dependencies, retry mechanisms, and monitoring dashboards, enabling efficient workflow management and execution.
What is the primary purpose of an Entity-Relationship Diagram (ERD)?
- Describing entity attributes
- Identifying primary keys
- Representing data types
- Visualizing the relationships between entities
The primary purpose of an Entity-Relationship Diagram (ERD) is to visually represent the relationships between entities in a database model. This helps in understanding the structure and design of the database.
What is the difference between a unique index and a non-unique index?
- A non-unique index allows duplicate values in the indexed column(s)
- A non-unique index does not allow NULL values in the indexed column(s)
- A unique index allows NULL values in the indexed column(s)
- A unique index allows only unique values in the indexed column(s)
A unique index enforces uniqueness, ensuring that each indexed value is unique, while a non-unique index allows duplicate values to be stored. Understanding this difference is crucial for data integrity and query optimization.
________ is a technique used in Dimensional Modeling to handle changes to dimension attributes over time.
- Fast Updating Dimension (FUD)
- Quick Altering Dimension (QAD)
- Rapidly Changing Dimension (RCD)
- Slowly Changing Dimension (SCD)
Slowly Changing Dimension (SCD) is a technique used in Dimensional Modeling to handle changes to dimension attributes over time. It involves maintaining historical data to accurately reflect changes in dimension attributes.
________ is a NoSQL database that is optimized for high availability and partition tolerance, sacrificing consistency under certain circumstances.
- Cassandra
- MongoDB
- Neo4j
- Redis
Cassandra is a NoSQL database designed for high availability and partition tolerance in distributed environments. It follows the principles of the CAP theorem, prioritizing availability and partition tolerance over consistency in certain scenarios.
In an ERD, a ________ is a property or characteristic of an entity.
- Attribute
- Entity
- Key
- Relationship
An attribute in an ERD represents a property or characteristic of an entity. It describes the data that can be stored for each instance of the entity, contributing to the overall definition of the entity's structure.
What is a Slowly Changing Dimension (SCD) in Dimensional Modeling?
- A dimension that changes at a regular pace
- A dimension that changes frequently over time
- A dimension that changes unpredictably over time
- A dimension that rarely changes over time
A Slowly Changing Dimension (SCD) in Dimensional Modeling is a dimension that changes over time but not frequently. It typically records historical data, preserving the history of changes in the dimension.