January 2019
Beginner
556 pages
14h 19m
English
Content preview from Learning PostgreSQL 11 - Third Edition
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Relational algebra
Relational algebra is the formal language of the relational model. It defines a set of closed operations over relations, that is, the result of each operation is a new relation. Relational algebra inherits many operators from set algebra. Relational algebra operations can be categorized into two groups:
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The first one is a group of operations that are inherited from set theory such as UNION, intersection, set difference, and Cartesian product, also known as cross product.
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The second is a group of operations that are specific to the relational model such as SELECT and PROJECT. Relational algebra operations could also be classified as binary and unary operations.
The primitive operators are as follows:
- SELECT (σ): ...
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