What is a transitive dependency in the context of normalization?
- Dependency between non-prime attributes
- Dependency where a non-prime attribute determines a prime attribute
- Dependency where a non-prime attribute determines another non-prime attribute
- Dependency where a prime attribute determines another prime attribute
In normalization, a transitive dependency occurs when a non-prime attribute determines another non-prime attribute. It violates the principles of normalization, and resolving such dependencies is crucial for achieving higher normal forms.
Which type of dimension change captures historical data without overwriting existing records?
- Type 1
- Type 2
- Type 3
- Type 4
Type 2 dimension change captures historical data without overwriting existing records. It adds new records for each change, including a surrogate key and an effective date range, allowing for historical analysis while preserving the original data.
_______ is the process of physically grouping related data together to improve query performance and reduce disk I/O.
- Data Clustering
- Data Encryption
- Data Serialization
- Data Validation
Data Clustering involves physically grouping related data together in storage. This process helps improve query performance by reducing the need for extensive disk I/O operations when retrieving related data. It enhances the efficiency of data retrieval operations, especially in scenarios where related data is commonly accessed together.
_______ techniques in Dimensional Modeling aim to improve query performance by pre-calculating and storing aggregated data.
- Aggregation
- Indexing
- Normalization
- Partitioning
Aggregation techniques in Dimensional Modeling involve pre-calculating and storing aggregated data to enhance query performance. This reduces the need for complex computations during queries, making analytical processing faster and more efficient in data warehouses.
What factors should be considered when choosing the appropriate Slowly Changing Dimensions (SCD) technique for a data warehouse?
- Availability of primary keys
- Database normalization level
- Number of tables in the database
- Volume of data changes, Query performance, and Data storage requirements
Choosing the appropriate SCD technique involves considering factors such as the volume of data changes, query performance, and data storage requirements. Each type of SCD has its strengths and weaknesses, and the decision should align with the specific needs and characteristics of the data warehouse environment.
What is a key characteristic of document databases in terms of schema flexibility?
- Dynamic schema
- Fixed schema
- Relational schema
- Semi-structured schema
A key characteristic of document databases is their dynamic schema. Unlike traditional relational databases with fixed schemas, document databases allow for flexible schema designs where each document can have its own unique structure. This flexibility accommodates evolving data requirements and simplifies the development process.
Scenario: A company has employees and projects. An employee can work on multiple projects, and a project can have multiple employees working on it. Which type of relationship would you use to represent this scenario in an ERD?
- Many-to-Many
- Many-to-One
- One-to-Many
- One-to-One
In this scenario, a Many-to-Many relationship is appropriate. This allows each employee to work on multiple projects, and each project to have multiple employees associated with it. It involves a junction table to manage the relationship.
In an ERD, an _______ key is a key that consists of more than one attribute.
- Composite
- Foreign
- Primary
- Unique
In an ERD, a composite key is a key that consists of more than one attribute. It is used to uniquely identify an entity when a single attribute is not sufficient. Composite keys are common in situations where a combination of attributes is needed for uniqueness.
What is aggregation in the context of data modeling?
- Breaking down a large dataset into smaller pieces
- Combining multiple entities into a single entity
- Creating relationships between entities
- Summarizing and combining data at a higher level
Aggregation in data modeling involves summarizing and combining data at a higher level. It is used to provide insights into the overall trends and patterns within a dataset, often involving the use of aggregation functions like SUM, AVG, COUNT, etc., to analyze and present data in a more meaningful way.
What strategies can be employed to ensure data consistency across partitions?
- Consistent hashing
- Eventual consistency
- Two-phase commit protocol
- Vector clocks for timestamp ordering
Strategies like the Two-phase commit protocol can be employed to ensure data consistency across partitions in distributed databases. This involves a coordinated approach to commit or abort transactions across all nodes, ensuring that data remains consistent even in a distributed environment.