Question: Which one of the following is commonly used to define the overall design of the database?
Entity-relationship diagram (ERD) is commonly used to define the overall design of the database. An ERD is a graphical representation of the entities, attributes, and relationships between entities in a database. It is a high-level view of the database that is used to design the database and to communicate the design to users.
The other options are:
- Data flow diagram (DFD): A DFD is a graphical representation of the flow of data through a system. It is used to model the system's functionality and to identify the different components of the system.
- Use case diagram: A use case diagram is a graphical representation of the interactions between users and a system. It is used to identify the different use cases for the system and to define the system's requirements.
- Class diagram: A class diagram is a graphical representation of the classes and relationships between classes in a software system. It is used to model the system's design and to communicate the design to developers.
ERDs are the most commonly used tool for database design because they are easy to understand and use. They can be used to model complex databases and to communicate the design to users from different backgrounds.
Here is an example of a simple ERD:
Entity: Customer
Attributes: CustomerID, FirstName, LastName, Email
Entity: Order
Attributes: OrderID, CustomerID, OrderDate, TotalAmount
Relationship: Customer places orders
This ERD shows that there are two entities in the database: Customer and Order. The Customer entity has the attributes CustomerID, FirstName, LastName, and Email. The Order entity has the attributes OrderID, CustomerID, OrderDate, and TotalAmount. The Customer places orders relationship shows that a Customer can place multiple Orders, but an Order can only be placed by one Customer.
ERDs can be used to model more complex databases with multiple entities and relationships. They are an essential tool for database design and for communicating the design to users.
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