10 Questions
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?
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?
Because many people can have the same name
What is an example of a key in a real-world scenario?
National ID Card number
What is an entity type?
A category or class of entities with similar characteristics
What is the difference between an entity type and an instance?
An entity type is a category, while an instance is a specific example of that category
Why do we need keys in data management?
To uniquely identify and access a particular instance within a large dataset
Can a combination of attributes be used as a key?
Yes
What is the significance of a key in data retrieval?
It enables precise identification of a single instance
What is the relationship between an entity type and its instances?
An entity type can have many instances
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]
Learn about entity types, attributes, and keys in database management. Understand how keys help identify and access specific entity instances.
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