Section 2 Oracle Acad

This statement is true because data models are visual representations of the data that will be stored in a database. These models help users understand the structure and organization of the data in the system. The data listed on the diagram represents the actual data that can be entered into the database. Therefore, any data not listed on the diagram cannot be entered into the database.

Foreign keys are used to create relationships between tables in the relational model. A foreign key is a column or a set of columns in one table that refers to the primary key in another table. This establishes a link between the two tables and allows for the enforcement of referential integrity. By using foreign keys, data integrity can be maintained and relationships can be established between tables, ensuring consistency and accuracy in the database.

The correct answer is "Distinguish one instance of an entity from all other instances of that entity." Unique identifiers are used to differentiate one specific occurrence or instance of an entity from all other occurrences or instances of the same entity. They provide a way to uniquely identify and distinguish individual records or objects within a database, ensuring that no two instances are the same.

Flat file databases do not avoid data duplication. In fact, they often contain redundant copies of data, which can lead to inefficiency and inconsistency. Flat file databases store data in a simple, text-based format where each line represents a record and each field is separated by a delimiter. This structure does not provide mechanisms to prevent or manage data duplication. Relational databases, on the other hand, use normalization techniques and enforce data integrity constraints to eliminate redundancy and ensure data consistency.

An attribute is a piece of information that describes an entity. It is a property of the entity and can be used to quantify, qualify, classify, or specify the entity. In a database or data model, attributes are used to define the characteristics or properties of an entity. They provide additional details and context about the entity, allowing for better organization and understanding of the data.

The given statement is false. Each column in a relation is not called an entity. In a relation, each column represents an attribute or a characteristic of the entity, while each row represents a specific instance or record of the entity. The entity itself is represented by the entire relation or table, not by individual columns.

In a physical data model, an attribute is represented as a column. A column is a vertical structure in a table that holds the specific data for that attribute. It represents a specific characteristic or property of the entity being modeled. Each column is labeled with a unique name and has a defined data type, allowing it to store specific types of data. Columns in a physical data model are used to organize and store data in a relational database system.

In a barred relationship, the primary key column is not mapped on the many side. Instead, it is mapped on the one side. This means that the primary key column is present in the table representing the "one" side of the relationship, rather than the table representing the "many" side. Therefore, the correct answer is false.

A unique identifier serves the purpose of identifying a single, distinct instance of an entity by utilizing one or more attributes and/or relationships. It allows for differentiation between multiple entities and ensures that each instance can be uniquely identified. This helps in organizing and managing data effectively, as well as facilitating efficient retrieval and referencing of specific entities within a system or database.

Data modeling is performed for the following reasons: The ERD becomes a blueprint for designing the actual system. It helps discussions and reviews. Creating an ERD serves as a visual representation of the system and allows stakeholders to understand and provide feedback on the proposed design. It also serves as a guide for developers to implement the system accurately. Without data modeling, there is a higher chance of miscommunication and errors during the development process.

The online clothing store, online book store, and online personal shopping service are examples of e-businesses that use database software. These businesses require a database to store and manage their inventory, customer information, and transaction records. The database software allows them to efficiently organize and retrieve data, track sales, and provide personalized shopping experiences for their customers.

In one-to-one relationships, the primary key of one table is used as a foreign key in another table. This is done to establish a connection between the two tables. However, in the given statement, it is mentioned that one-to-one relationships are transformed into foreign keys in both tables created for that relationship. This is incorrect. In a one-to-one relationship, the foreign key is only added in one of the tables, not in both. Therefore, the correct answer is false.

Attributes are characteristics or properties that describe, qualify, quantify, classify, or specify an entity. They can be single valued if they belong to only one entity or can be multi-valued if they belong to more than one entity. Attributes can often be adjectives that provide additional information about the entity. Additionally, attributes have a data type, such as number or character string, to define the kind of data that can be stored in them.

A primary key is not required for a table. While it is recommended to have a primary key to uniquely identify each record in a table, it is not mandatory. Tables can still function without a primary key, but it may make it more difficult to manage and manipulate the data within the table.

Conceptual models are created for several reasons. Firstly, they model functional and informational needs, which means they help identify the requirements and specifications of a system or process. Secondly, they capture current and future needs, allowing for the consideration of potential changes and improvements. Lastly, they accurately describe what a physical model will contain, providing a clear representation of the data and information flow within the system. These reasons demonstrate the importance of conceptual models in understanding and designing complex systems.