What are primary keys, composite primary keys, candidate keys, and alternate keys in relational databases?
Understand the Problem
The question pertains to relational databases, specifically discussing key concepts such as primary keys, composite primary keys, candidate keys, and alternate keys. It aims to clarify how these keys function within database tables to uniquely identify tuples, along with their definitions and examples.
Answer
Primary Key: Unique identifier. Composite: Multiple attributes. Candidate: Can be primary. Alternate: Unused candidate.
Primary Key: Uniquely identifies each tuple within a relation. Composite Primary Key: A primary key made of two or more attributes. Candidate Key: Attributes that can qualify as a primary key. Alternate Key: Candidate keys not chosen as the primary key.
Answer for screen readers
Primary Key: Uniquely identifies each tuple within a relation. Composite Primary Key: A primary key made of two or more attributes. Candidate Key: Attributes that can qualify as a primary key. Alternate Key: Candidate keys not chosen as the primary key.
More Information
Keys are crucial in relational databases to ensure data integrity. Each type of key plays a distinct role in identifying and managing data relationships within tables.
Tips
Common mistakes include confusing candidate keys with primary keys and not recognizing that a composite key is still a primary key if it uniquely identifies rows.
Sources
- Types of Keys in Relational Model - geeksforgeeks.org
- Database Keys Made Easy - Primary, Foreign, Candidate - youtube.com
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