Higher Computing Revision - Database Design

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What is an entity in database design?

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An entity is a person, place, thing, event, or concept of interest to the business or organization about which data is to be stored. Examples include Student, Teacher, Class, and Subject.

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What is an entity occurrence?

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An entity occurrence is a specific example of an entity, also known as an instance. For example, John Smith is an entity occurrence in the Student entity.

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What is an attribute in the context of database design?

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An attribute is a characteristic of an entity. For example, attributes of the Student entity include studentID, firstname, surname, and dateOfBirth.

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Define primary key.

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A primary key is an attribute or combination of attributes that uniquely identifies one, and only one, record in a table. For example, studentID is the primary key of the Student entity.

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What is a foreign key?

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A foreign key is an attribute in one table that uniquely identifies a row of another table where it is a primary key. It creates a link between two tables.

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Explain compound key.

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A compound key is a primary key that comprises two or more attributes. Each attribute in a compound key is a primary key in its own right.

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What is a relationship in database design?

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A relationship is a natural association between one or more entities, such as Students learning Subjects or Teachers educating Students.

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Describe an entity-occurrence diagram.

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An entity-occurrence diagram illustrates the relationships between the entity occurrences of one entity with those within a related entity, helping to identify the cardinality of the relationship.

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What is an entity-relationship diagram?

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An entity-relationship diagram is a graphical representation of the entities in a system, summarizing the relationships between two or more entities.

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Define cardinality in the context of database relationships.

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Cardinality defines the number of participants in a relationship, indicating how many entity occurrences in one entity are associated with occurrences in a related entity.