What is the purpose of a check constraint in a database schema?
- Defines relationships between tables
- Enforces unique values in a column
- Sets default values for columns
- Validates data against a specified condition
A check constraint in a database schema is used to validate data against a specified condition. It ensures that values in a column meet specific criteria, providing a way to control and maintain data integrity.
Which type of database is commonly associated with document-based modeling?
- Hierarchical Database
- NoSQL Database
- Object-Oriented Database
- Relational Database
Document-based modeling is commonly associated with NoSQL databases. Unlike traditional relational databases, NoSQL databases, especially document stores, allow for the storage and retrieval of unstructured or semi-structured data, making them well-suited for document-based modeling.
In a Star Schema, the fact table is surrounded by _______ tables.
- Dimension
- Lookup
- Reference
- Satellite
In a Star Schema, the fact table is surrounded by Dimension tables. Dimension tables contain descriptive attributes and provide context to the measurements stored in the fact table. This design enhances query performance by simplifying joins and optimizing data retrieval for analytical queries.
An _______ relationship allows a single entity to inherit properties from multiple superclasses.
- Aggregation
- Association
- Dependency
- Inheritance
An Inheritance relationship allows a single entity to inherit properties from multiple superclasses. It is a key concept in object-oriented data modeling, enabling the creation of a more flexible and reusable data model.
The _______ statement in SQL is used to retrieve data from a database.
- DELETE
- INSERT
- SELECT
- UPDATE
The SELECT statement in SQL is used to retrieve data from a database. It allows you to specify the columns you want to retrieve and the conditions for selecting specific rows. This statement is fundamental for querying and extracting information from a database.
How does a many-to-many relationship affect the database schema?
- It doesn't impact the schema
- It eliminates the need for foreign keys
- It requires the use of a junction table
- It simplifies the schema structure
A many-to-many relationship affects the database schema by necessitating the use of a junction table. This table resolves the complexity of such relationships by breaking them down into two one-to-many relationships, linking the original entities through an intermediary table.
Type 3 Slowly Changing Dimensions (SCD) stores only the _______ value and the _______ value in the dimension table.
- current, original
- current, previous
- latest, former
- new, old
In Type 3 Slowly Changing Dimensions (SCD), only the current value and the previous value are stored in the dimension table. This allows for limited historical tracking by capturing the immediate previous state of the dimension attribute.
In Forward Engineering, what is the initial step after creating a conceptual data model?
- Create a logical data model
- Design the user interface
- Generate a physical data model
- Optimize the database schema
After creating a conceptual data model in Forward Engineering, the next step is to generate a logical data model. The logical data model further refines the structure and relationships before moving on to the creation of the physical data model.
Collaboration features in ER diagram tools facilitate _______ among team members.
- Code writing
- Communication
- Data manipulation
- Documentation
Collaboration features in ER diagram tools are designed to facilitate communication among team members. This may include features like comments, annotations, and real-time collaboration, allowing team members to work together effectively on designing and refining the database structure.
How does cardinality affect database design and query performance?
- Cardinality is only relevant in certain types of databases
- Higher cardinality leads to more complex database designs and slower query performance
- It has no impact on database design or query performance
- Lower cardinality simplifies database design but may impact query performance
Cardinality significantly affects database design and query performance. Lower cardinality simplifies database design, but it may impact query performance negatively. Higher cardinality leads to more complex designs and potentially slower query performance. Striking the right balance is crucial for an efficient database.