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This chapter delves into the foundational concepts of relational algebra and calculus, focusing on unary and binary operations such as SELECT, PROJECT, JOIN, and DIVISION. It examines operations derived from set theory, including UNION, INTERSECTION, and CARTESIAN PRODUCT, alongside aggregate functions and recursive closures. The tuple and domain relational calculus are explored, covering essential concepts like tuple variables, quantifiers, and safe expressions. Through examples, the chapter illustrates how these operations form the basis for effective querying in relational databases.
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Chapter 6 The Relational Algebra and Relational Calculus
Unary Relational Operations: SELECT and PROJECT • The SELECT Operation • The PROJECT Operation • Sequences of Operations and the RENAME Operation
Relational Algebra Operations from Set Theory • The UNION, INTERSECTION, and MINUS Operations • The CARTESIAN PRODUCT (or CROSS PRODUCT) Operation
Binary Relational Operations: JOIN and DIVISION • The JOIN Operation • The EQUIJOIN and NATURAL JOIN Variations of JOIN • A Complete Set of Relational Algebra Operations • The DIVISION Operation
Additional Relational Operations • Aggregate Functions and Grouping • Recursive Closure Operations • OUTER JOIN Operations • The OUTER JOIN Operation
The Tuple Relational Calculus • Tuple Variables and Range Relations • Expressions and Formulas in Tuple Relational Calculus • The Existential and Universal Quantifiers • Example Queries Using the Existential Quantifier • Transforming the Universal and Existential Quantifiers • Using the Universal Quantifier • Safe Expressions