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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?
What is an entity type?
What is an entity type?
What is the difference between an entity type and an instance?
What is the difference between an entity type and an instance?
Why do we need keys in data management?
Why do we need keys in data management?
Can a combination of attributes be used as a key?
Can a combination of attributes be used as a key?
What is the significance of a key in data retrieval?
What is the significance of a key in data retrieval?
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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