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Questions and Answers
What is the role of keys in an entity type?
What is the role of keys in an entity type?
To identify or access a particular entity instance of an entity type
What is the primary function of a key in an entity type?
What is the primary function of a key in an entity type?
To pick a particular/single instance out of many instances
Why can't we use a single attribute like 'name' to identify an entity instance?
Why can't we use a single attribute like 'name' to identify an entity instance?
Because many people can have the same name
What is an example of a key in a real-world scenario?
What is an example of a key in a real-world scenario?
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What is an entity type?
What is an entity type?
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What is the difference between an entity type and an instance?
What is the difference between an entity type and an instance?
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Why do we need keys in data management?
Why do we need keys in data management?
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Can a combination of attributes be used as a key?
Can a combination of attributes be used as a key?
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What is the significance of a key in data retrieval?
What is the significance of a key in data retrieval?
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What is the relationship between an entity type and its instances?
What is the relationship between an entity type and its instances?
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Study Notes
Entity Types and Attributes
- Entity types are differentiated by their attributes.
- Each entity type can have multiple instances, with each instance having values for each attribute.
Keys and Their Purpose
- A key is a set of attributes that identifies a specific entity instance within an entity type.
- Keys are necessary to access and identify a particular instance among many instances of an entity type.
- Example: In a database of Pakistan's population, a key is needed to identify a specific person among millions.
Characteristics of Keys
- A key can be simple (consisting of a single attribute) or composite (consisting of two or more attributes).
- Keys can be drawn from existing attributes in the real-world system or designed by the database designer.
Types of Keys
- Super Key: [no additional information provided]
- Candidate Key: [no additional information provided]
- Primary Key: [no additional information provided]
- Alternate Key: [no additional information provided]
- Secondary Key: [no additional information provided]
- Foreign Key: [no additional information provided]
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Description
Learn about entity types, attributes, and keys in database management. Understand how keys help identify and access specific entity instances.
