Friday, 27 June 2014

Relational Algebra in Database management system | Relational Model


It is the collection of operations used to manipulate a relations or tables.These operations enables the user to specify the retrieval request on one or more relations that result in a new relation without changing the original relation.It is a procedural language.The user has to specify what is required and what are the sequence of steps to get the desired output.

Relational Closure- When operations are performed on existing relations to produce a new relation then the original relation remains unaffected. Therefore the output from one operation can become the input of some other operation.This property is called relational closure.

TYPES OF RELATIONAL OPERATIONS- There are two types of relational operations
1.) Traditional Set operations or Basic Set oriented operations
2.) Special relational Operations

1.) Traditional Set operations or Basic Set oriented operations- 
These include Union,integration ,difference and Cartesian product.These are the binary operations, it means that these can be applied to a pair of relations.

2.) Special relational Operations-
These includes operations like
  • Selection
  • Projection
  • Join
  • Division  
where selection and projection are unary operations and Join and division are binary operations.


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