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Join

Represents a relational join operator commonly used in database theory and set operations.

Overview

Essential in mathematical logic, relational algebra, and database theory for combining relations or sets based on common attributes or conditions.

  • Frequently used in formal database query representations and theoretical computer science.
  • Appears in academic papers and textbooks discussing relational databases and set theory.
  • Serves as a fundamental notation in expressing database operations and relationships between tables.
  • Often encountered alongside other relational operators in mathematical expressions describing data transformations.

Examples

Natural join operation between database relations R and S.

R⋈SR \Join S 
R \Join S

Multiple relation joins in database algebra.

R⋈S⋈TR \Join S \Join T 
R \Join S \Join T

Join with explicit attribute conditions in relational algebra.

(σage>25(R))⋈S(\sigma_{age > 25}(R)) \Join S 
(\sigma_{age > 25}(R)) \Join S