Understanding Entities and Attributes in Database Modelling

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What is an entity in the context of database modelling?

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An entity is information of significance which the business needs to keep, and in database terms, it refers to something that can be stored and retrieved, such as a person, place, event, or thing.

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Can you name some common entities?

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Common entities include Employee, Invoice, and Supplier.

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What is an attribute?

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An attribute is a characteristic of an entity. For example, Expiry Date is an attribute of a Food Item entity.

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What is the purpose of drawing an entity diagram?

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The purpose of drawing an entity diagram is to visually represent entities and their attributes, using notations like Barker's Notation and Crow's Foot notation.

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What is Barker's Notation?

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Barker's Notation is a method used for diagramming entities and their attributes in database modelling.

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What should the entity name in a diagram represent?

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The entity name must be unique and meaningful to everyone working with the system, written in uppercase inside the entity's soft box.

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How should attribute names be formatted in a diagram?

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Attribute names should be written in lowercase and can be combined into more than one word, but they are often omitted from the diagram for clarity.

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What is an instance of an entity?

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An instance of an entity is a specific real-world example of that entity, such as John Doe being an instance of the LEARNER entity.

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What is a Unique Identifier (UID)?

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A Unique Identifier (UID) is an attribute or set of attributes that uniquely identifies an instance of an entity, such as an employee number.

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Why is it important to identify a unique instance of an entity?

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Identifying a unique instance is crucial for retrieving specific information from a database, ensuring that the correct data is accessed.