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the ____ defines a set of operations on relations, paralleling the usual algebraic operations such as addition, subtraction or multiplication, which operates on numbers.

(a) Relational Calculas

(b) Referential Integrity

(c) Relational Algebra

(d) Relations
in Databases
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@mohit+jain

 

©  Relational Algebra ….

 

Relational algebra is a procedural query language, which takes instances of relations as input and yields instances of relations as output…. It uses operators to perform queries…

An operator can be either unary or binary. They accept relations as their input and yield relations as their output….

 

The fundamental operations of relational algebra –

 

Select

Project

Union                  – Equivalent to addition

Set difference       –Equivalent to subtraction

Cartesian Product  – Equivalent to multiplication

Rename

 

 

 

Important Point:

 

Difference between relational algebra and relational calculus is that relational calculus is non-procedural…..

It tells what to do but cannot explain how to do it…..